08-29-2020, 11:30 AM
Python One Line Append
<div><p>Do you want to <a href="https://blog.finxter.com/python-one-line-x/" target="_blank" rel="noreferrer noopener" title="Python One Line X">one-linerize</a> the <code>append()</code> method in Python? I feel you—writing short and concise one-liners can be an addiction! <img src="https://s.w.org/images/core/emoji/12.0.0-1/72x72/1f642.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" /></p>
<p>This article will teach you all the ways to append one or more elements to a list in a single line of Python code!</p>
<h2>Python List Append</h2>
<p>Let’s quickly recap the append method that allows you add an arbitrary element to a given list.</p>
<figure class="wp-block-embed-youtube wp-block-embed is-type-rich is-provider-embed-handler wp-embed-aspect-16-9 wp-has-aspect-ratio">
<div class="wp-block-embed__wrapper">
<div class="ast-oembed-container"><iframe title="Python List append() Method" width="1400" height="788" src="https://www.youtube.com/embed/0fteTqtUUik?feature=oembed" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe></div>
</p></div>
</figure>
<p>How can you add an elements to a given list? Use the <code>append()</code> method in Python.</p>
<p><strong>Definition and Usage</strong></p>
<p>The <code>list.append(x)</code> method—as the name suggests—appends element <code>x</code> to the end of the <code>list</code>. </p>
<p>Here’s a short example:</p>
<pre class="EnlighterJSRAW" data-enlighter-language="generic" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">>>> l = []
>>> l.append(42)
>>> l
[42]
>>> l.append(21)
>>> l
[42, 21]</pre>
<p>In the first line of the example, you create the list <code>l</code>. You then append the integer element <code>42</code> to the end of the list. The result is the list with one element <code>[42]</code>. Finally, you append the integer element <code>21</code> to the end of that list which results in the list with two elements <code>[42, 21]</code>. </p>
<p><strong>Syntax</strong></p>
<p>You can call this method on each list object in Python. Here’s the syntax:</p>
<p><code>list.append(element)</code></p>
<p><strong>Arguments</strong></p>
<figure class="wp-block-table is-style-stripes">
<table>
<thead>
<tr>
<th>Argument</th>
<th>Description</th>
</tr>
</thead>
<tbody>
<tr>
<td><code>element</code></td>
<td>The object you want to append to the list.</td>
</tr>
</tbody>
</table>
</figure>
<p><strong>Related articles:</strong></p>
<ul>
<li><a href="https://blog.finxter.com/python-lists/" target="_blank" rel="noreferrer noopener">The Ultimate Guide to Python Lists</a></li>
<li><a href="https://blog.finxter.com/python-list-append/" target="_blank" rel="noreferrer noopener" title="Python List append() Method">List.append() method — A Simple Illustrated Guide</a></li>
</ul>
<h2>Python One Line List Append</h2>
<p><strong>Problem</strong>: How can you <a href="https://blog.finxter.com/how-to-create-a-python-list/" title="How to Create a Python List?" target="_blank" rel="noreferrer noopener">create a list</a> and append an element to a list using only <a href="https://pythononeliners.com/" target="_blank" rel="noreferrer noopener" title="https://pythononeliners.com/">one line</a> of Python code? </p>
<p>You may find this challenging because you must accomplish two things in one line: (1) creating the list and (2) appending an element to it.</p>
<p><strong>Solution</strong>: We use the standard technique to one-linerize each “flat” multi-line code snippet: with the semicolon as a separator between the expressions.</p>
<pre class="EnlighterJSRAW" data-enlighter-language="generic" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">a = [1, 2, 3]; a.append(42); print(a)</pre>
<p>This way, we accomplish three things in a single line of Python code:</p>
<ul>
<li>Creating the <a href="https://blog.finxter.com/python-lists/" target="_blank" rel="noreferrer noopener" title="The Ultimate Guide to Python Lists">list </a><code>[1, 2, 3]</code> and assigning it to the variable <code>a</code>.</li>
<li>Appending the element 42 to the list referred to by <code>a</code>.</li>
<li><a href="https://blog.finxter.com/the-separator-and-end-arguments-of-the-python-print-function/" target="_blank" rel="noreferrer noopener" title="Python Print Function [And Its SECRET Separator & End Arguments]">Printing </a>the list to the shell.</li>
</ul>
<p><strong>Related Article: </strong><a href="https://blog.finxter.com/python-one-line-to-multiple-lines/" target="_blank" rel="noreferrer noopener" title="Python One Line to Multiple Lines">Python One Line to Multiple Lines</a></p>
<h2>Python One Line For Append</h2>
<p><strong>Problem</strong>: How can we append multiple elements to a list in a for loop but using only a single line of Python code?</p>
<p><strong>Example</strong>: Say, you want to filter a list of words against another list and store the resulting words in a new list using the append() method in a for loop. </p>
<pre class="EnlighterJSRAW" data-enlighter-language="generic" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group=""># FINXTER TUTORIAL:
# How to filter a list of words? words = ['hi', 'hello', 'Python', 'a', 'the']
stop_words = {'a', 'the'}
filtered_words = [] for word in words: if word not in stop_words: filtered_words.append(word) print(filtered_words)
# ['hi', 'hello', 'Python']
</pre>
<p>You first create a list of words to be filtered and stored in an initially empty list <code>filtered_words</code>. Second, you create a <a href="https://blog.finxter.com/sets-in-python/" title="The Ultimate Guide to Python Sets – with Harry Potter Examples">set </a>of stop words against you want to check the words in the list. Note that it’s far more efficient to use the set data structure for this because <a href="https://blog.finxter.com/complexity-of-python-operations/" target="_blank" rel="noreferrer noopener" title="Complexity of Python Operations">checking membership in sets is much faster </a>than checking membership in lists. <a href="https://blog.finxter.com/sets-in-python/" target="_blank" rel="noreferrer noopener" title="The Ultimate Guide to Python Sets – with Harry Potter Examples">See this tutorial for a full guide on Python sets.</a></p>
<p>You now iterate over all elements in the list <code>words</code> and add them to the <code>filtered_words</code> list if they are not in the set <code>stop_words</code>. </p>
<p><strong>Solution</strong>: You can one-linerize this filtering process using the following code:</p>
<pre class="EnlighterJSRAW" data-enlighter-language="generic" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">filtered_words = [word for word in words if word not in stop_words]</pre>
<p>The solution uses <a href="https://blog.finxter.com/list-comprehension/" title="List Comprehension in Python — A Helpful Illustrated Guide">list comprehension</a> to, essentially, create a <a href="https://blog.finxter.com/python-one-line-for-loop-a-simple-tutorial/" title="Python One Line For Loop [A Simple Tutorial]">single-line for loop</a>. </p>
<p>Here’s the complete code that solves the problem using the one-liner filtering method:</p>
<pre class="EnlighterJSRAW" data-enlighter-language="generic" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group=""># FINXTER TUTORIAL:
# How to filter a list of words? words = ['hi', 'hello', 'Python', 'a', 'the']
stop_words = {'a', 'the'}
filtered_words = [word for word in words if word not in stop_words] print(filtered_words)
# ['hi', 'hello', 'Python']</pre>
<p>Here’s a short tutorial on filtering in case you need more explanations:</p>
<p><strong>Related Article</strong>:<a href="https://blog.finxter.com/how-to-filter-a-list-in-python/" target="_blank" rel="noreferrer noopener" title="How to Filter a List in Python?"> How to Filter a List in Python?</a></p>
<h2>Python One Line If Append</h2>
<p>In the previous example, you’ve already seen how to use the if statement in the list comprehension statement to append more elements to a list if they full-fill a given condition. </p>
<p>How can you filter a list in Python using an arbitrary condition? The most Pythonic and most performant way is to use list comprehension <code>[x for x in list if condition]</code> to filter all elements from a list. </p>
<figure class="wp-block-embed-youtube wp-block-embed is-type-video is-provider-youtube wp-embed-aspect-16-9 wp-has-aspect-ratio">
<div class="wp-block-embed__wrapper">
<div class="ast-oembed-container"><iframe title="How to Filter a List in Python?" width="1400" height="788" src="https://www.youtube.com/embed/3nG4TLkqzf8?feature=oembed" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe></div>
</div>
</figure>
<p><strong>Try It Yourself:</strong></p>
<p> <iframe src="https://repl.it/@finxter/filterlistpython?lite=true" scrolling="no" allowtransparency="true" allowfullscreen="true" sandbox="allow-forms allow-pointer-lock allow-popups allow-same-origin allow-scripts allow-modals" width="100%" height="400px" frameborder="no"></iframe> </p>
<p>The most Pythonic way of filtering a list—in my opinion—is the list comprehension statement <code>[x for x in list if condition]</code>. You can replace condition with any function of <code>x</code> you would like to use as a filtering condition. </p>
<p>For example, if you want to filter all elements that are smaller than, say, 10, you’d use the list comprehension statement <code>[x for x in list if x<10]</code> to create a new list with all list elements that are smaller than 10. </p>
<p>Here are three examples of filtering a list:</p>
<ul>
<li>Get elements smaller than eight: <code>[x for x in lst if x<8]</code>.</li>
<li>Get even elements: <code>[x for x in lst if x%2==0]</code>.</li>
<li>Get odd elements: <code>[x for x in lst if x%2]</code>.</li>
</ul>
<pre class="EnlighterJSRAW" data-enlighter-language="generic" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">lst = [8, 2, 6, 4, 3, 1] # Filter all elements <8
small = [x for x in lst if x<8]
print(small) # Filter all even elements
even = [x for x in lst if x%2==0]
print(even) # Filter all odd elements
odd = [x for x in lst if x%2]
print(odd)</pre>
<p>The output is:</p>
<pre class="EnlighterJSRAW" data-enlighter-language="generic" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group=""># Elements <8
[2, 6, 4, 3, 1] # Even Elements
[8, 2, 6, 4] # Odd Elements
[3, 1]</pre>
<p>This is the most efficient way of filtering a list and it’s also the most Pythonic one. If you look for alternatives though, keep reading because I’ll explain to you each and every nuance of filtering lists in Python in this comprehensive guide.</p>
<h2>Python Append One Line to File</h2>
<figure class="wp-block-embed-youtube wp-block-embed is-type-video is-provider-youtube wp-embed-aspect-16-9 wp-has-aspect-ratio">
<div class="wp-block-embed__wrapper">
<div class="ast-oembed-container"><iframe title="Python One-Liner: Write String to File" width="1400" height="788" src="https://www.youtube.com/embed/Kv7mdHFfiNM?feature=oembed" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe></div>
</div>
</figure>
<p><strong>Problem</strong>: Given a string and a filename. How to write the string into the file with filename using only a <a href="https://pythononeliners.com/" target="_blank" rel="noreferrer noopener" title="https://pythononeliners.com/">single line of Python code</a>?</p>
<p><strong>Example</strong>: You have filename <code>'hello.txt'</code> and you want to write string <code>'hello world!'</code> into the file.</p>
<pre class="EnlighterJSRAW" data-enlighter-language="generic" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">hi = 'hello world!'
file = 'hello.txt' # Write hi in file '''
# File: 'hello.txt':
hello world! '''</pre>
<p>How to achieve this? In this tutorial, you’ll learn four ways of doing it in a single line of code!</p>
<p>Here’s a quick overview in our interactive <a href="https://blog.finxter.com/how-to-embed-a-python-interpreter-in-your-website/" target="_blank" rel="noreferrer noopener" title="How to Embed a Python Interpreter in Your Website?">Python shell</a>:</p>
<p> <iframe src="https://repl.it/@finxter/writefilesingleline?lite=true" scrolling="no" allowtransparency="true" allowfullscreen="true" sandbox="allow-forms allow-pointer-lock allow-popups allow-same-origin allow-scripts allow-modals" width="100%" height="900px" frameborder="no"></iframe> </p>
<p><em><strong>Exercise</strong>: Run the code and check the file <code>'hello.txt'</code>. How many <code>'hello worlds!'</code> are there in the file? Change the code so that only one <code>'hello world!'</code> is in the file!</em></p>
<p>The most straightforward way is to use the <code><a href="https://docs.python.org/3/reference/compound_stmts.html#the-with-statement" target="_blank" rel="noreferrer noopener" title="https://docs.python.org/3/reference/compound_stmts.html#the-with-statement">with</a></code> statement in a single line (without line break). </p>
<pre class="EnlighterJSRAW" data-enlighter-language="generic" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">hi = 'hello world!'
file = 'hello.txt' # Method 1: 'with' statement
with open(file, 'a') as f: f.write(hi) '''
# File: 'hello.txt':
hello world! '''</pre>
<p>You use the following steps:</p>
<ul>
<li>The <code>with</code> environment makes sure that there are no side-effects such as open files.</li>
<li>The <code>open(file, 'a')</code> statement opens the file with filename <code>file</code> and <a href="https://blog.finxter.com/python-list-append/" target="_blank" rel="noreferrer noopener" title="Python List append() Method">appends </a>the text you write to the contents of the file. You can also use <code>open(file, <strong>'w'</strong>)</code> to overwrite the existing file content.</li>
<li>The new file returned by the <code>open()</code> statement is named <code>f</code>.</li>
<li>In the <code>with</code> body, you use the statement <code>f.write(string)</code> to write <code>string</code> into the file <code>f</code>. In our example, the string is <code>'hello world!'</code>. </li>
</ul>
<p>Of course, a prettier way to write this in two lines would be to use proper <a href="https://blog.finxter.com/pep-8-hanging-indentation-and-closing-brackets-in-python/" target="_blank" rel="noreferrer noopener" title="PEP 8: Hanging Indentation and Closing Brackets in Python">indentation</a>:</p>
<pre class="EnlighterJSRAW" data-enlighter-language="generic" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">with open(file, 'a') as f: f.write(hi)</pre>
<p>This is the most well-known way to write a string into a file. The big advantage is that you don’t have to close the file—the <code>with</code> environment does it for you! That’s why many coders consider this to be the most <a href="https://blog.finxter.com/python-crash-course/" target="_blank" rel="noreferrer noopener" title="Python Programming Tutorial [+Cheat Sheets]">Pythonic </a>way.</p>
<p>You can find more ways on my detailed blog article.</p>
<p><strong>Related Article:</strong> <a href="https://blog.finxter.com/python-one-liner-write-string-to-file/" target="_blank" rel="noreferrer noopener" title="Python One-Liner: Write String to File">Python One-Liner: Write String to File</a></p>
<h2>Python One-Liners Book</h2>
<p><strong>Python programmers will improve their computer science skills with these useful one-liners.</strong></p>
<figure class="wp-block-image size-medium is-resized"><a href="https://www.amazon.com/gp/product/B07ZY7XMX8" target="_blank" rel="noopener noreferrer"><img src="https://blog.finxter.com/wp-content/uploads/2020/06/3D_cover-1024x944.jpg" alt="Python One-Liners" class="wp-image-10007" width="512" height="472" srcset="https://blog.finxter.com/wp-content/uploads/2020/06/3D_cover-scaled.jpg 1024w, https://blog.finxter.com/wp-content/uplo...00x277.jpg 300w, https://blog.finxter.com/wp-content/uplo...68x708.jpg 768w" sizes="(max-width: 512px) 100vw, 512px" /></a></figure>
<p><a href="https://amzn.to/2WAYeJE" target="_blank" rel="noreferrer noopener" title="https://amzn.to/2WAYeJE"><em>Python One-Liners</em> </a>will teach you how to read and write “one-liners”: concise statements of useful functionality packed into a single line of code. You’ll learn how to systematically unpack and understand any line of Python code, and write eloquent, powerfully compressed Python like an expert.</p>
<p>The book’s five chapters cover tips and tricks, regular expressions, machine learning, core data science topics, and useful algorithms. Detailed explanations of one-liners introduce key computer science concepts and boost your coding and analytical skills. You’ll learn about advanced Python features such as list comprehension, slicing, lambda functions, regular expressions, map and reduce functions, and slice assignments. You’ll also learn how to:</p>
<p><strong>•</strong> Leverage data structures to solve real-world problems, like using Boolean indexing to find cities with above-average pollution<br /><strong>•</strong> Use NumPy basics such as array, shape, axis, type, broadcasting, advanced indexing, slicing, sorting, searching, aggregating, and statistics<br /><strong>•</strong> Calculate basic statistics of multidimensional data arrays and the K-Means algorithms for unsupervised learning<br /><strong>•</strong> Create more advanced regular expressions using grouping and named groups, negative lookaheads, escaped characters, whitespaces, character sets (and negative characters sets), and greedy/nongreedy operators<br /><strong>•</strong> Understand a wide range of computer science topics, including anagrams, palindromes, supersets, permutations, factorials, prime numbers, Fibonacci numbers, obfuscation, searching, and algorithmic sorting</p>
<p>By the end of the book, you’ll know how to write Python at its most refined, and create concise, beautiful pieces of “Python art” in merely a single line.</p>
<p><strong><a href="https://amzn.to/2WAYeJE" target="_blank" rel="noreferrer noopener" title="https://amzn.to/2WAYeJE"><em>Get your Python One-Liners Now!!</em></a></strong></p>
</div>
https://www.sickgaming.net/blog/2020/08/...ne-append/
<div><p>Do you want to <a href="https://blog.finxter.com/python-one-line-x/" target="_blank" rel="noreferrer noopener" title="Python One Line X">one-linerize</a> the <code>append()</code> method in Python? I feel you—writing short and concise one-liners can be an addiction! <img src="https://s.w.org/images/core/emoji/12.0.0-1/72x72/1f642.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" /></p>
<p>This article will teach you all the ways to append one or more elements to a list in a single line of Python code!</p>
<h2>Python List Append</h2>
<p>Let’s quickly recap the append method that allows you add an arbitrary element to a given list.</p>
<figure class="wp-block-embed-youtube wp-block-embed is-type-rich is-provider-embed-handler wp-embed-aspect-16-9 wp-has-aspect-ratio">
<div class="wp-block-embed__wrapper">
<div class="ast-oembed-container"><iframe title="Python List append() Method" width="1400" height="788" src="https://www.youtube.com/embed/0fteTqtUUik?feature=oembed" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe></div>
</p></div>
</figure>
<p>How can you add an elements to a given list? Use the <code>append()</code> method in Python.</p>
<p><strong>Definition and Usage</strong></p>
<p>The <code>list.append(x)</code> method—as the name suggests—appends element <code>x</code> to the end of the <code>list</code>. </p>
<p>Here’s a short example:</p>
<pre class="EnlighterJSRAW" data-enlighter-language="generic" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">>>> l = []
>>> l.append(42)
>>> l
[42]
>>> l.append(21)
>>> l
[42, 21]</pre>
<p>In the first line of the example, you create the list <code>l</code>. You then append the integer element <code>42</code> to the end of the list. The result is the list with one element <code>[42]</code>. Finally, you append the integer element <code>21</code> to the end of that list which results in the list with two elements <code>[42, 21]</code>. </p>
<p><strong>Syntax</strong></p>
<p>You can call this method on each list object in Python. Here’s the syntax:</p>
<p><code>list.append(element)</code></p>
<p><strong>Arguments</strong></p>
<figure class="wp-block-table is-style-stripes">
<table>
<thead>
<tr>
<th>Argument</th>
<th>Description</th>
</tr>
</thead>
<tbody>
<tr>
<td><code>element</code></td>
<td>The object you want to append to the list.</td>
</tr>
</tbody>
</table>
</figure>
<p><strong>Related articles:</strong></p>
<ul>
<li><a href="https://blog.finxter.com/python-lists/" target="_blank" rel="noreferrer noopener">The Ultimate Guide to Python Lists</a></li>
<li><a href="https://blog.finxter.com/python-list-append/" target="_blank" rel="noreferrer noopener" title="Python List append() Method">List.append() method — A Simple Illustrated Guide</a></li>
</ul>
<h2>Python One Line List Append</h2>
<p><strong>Problem</strong>: How can you <a href="https://blog.finxter.com/how-to-create-a-python-list/" title="How to Create a Python List?" target="_blank" rel="noreferrer noopener">create a list</a> and append an element to a list using only <a href="https://pythononeliners.com/" target="_blank" rel="noreferrer noopener" title="https://pythononeliners.com/">one line</a> of Python code? </p>
<p>You may find this challenging because you must accomplish two things in one line: (1) creating the list and (2) appending an element to it.</p>
<p><strong>Solution</strong>: We use the standard technique to one-linerize each “flat” multi-line code snippet: with the semicolon as a separator between the expressions.</p>
<pre class="EnlighterJSRAW" data-enlighter-language="generic" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">a = [1, 2, 3]; a.append(42); print(a)</pre>
<p>This way, we accomplish three things in a single line of Python code:</p>
<ul>
<li>Creating the <a href="https://blog.finxter.com/python-lists/" target="_blank" rel="noreferrer noopener" title="The Ultimate Guide to Python Lists">list </a><code>[1, 2, 3]</code> and assigning it to the variable <code>a</code>.</li>
<li>Appending the element 42 to the list referred to by <code>a</code>.</li>
<li><a href="https://blog.finxter.com/the-separator-and-end-arguments-of-the-python-print-function/" target="_blank" rel="noreferrer noopener" title="Python Print Function [And Its SECRET Separator & End Arguments]">Printing </a>the list to the shell.</li>
</ul>
<p><strong>Related Article: </strong><a href="https://blog.finxter.com/python-one-line-to-multiple-lines/" target="_blank" rel="noreferrer noopener" title="Python One Line to Multiple Lines">Python One Line to Multiple Lines</a></p>
<h2>Python One Line For Append</h2>
<p><strong>Problem</strong>: How can we append multiple elements to a list in a for loop but using only a single line of Python code?</p>
<p><strong>Example</strong>: Say, you want to filter a list of words against another list and store the resulting words in a new list using the append() method in a for loop. </p>
<pre class="EnlighterJSRAW" data-enlighter-language="generic" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group=""># FINXTER TUTORIAL:
# How to filter a list of words? words = ['hi', 'hello', 'Python', 'a', 'the']
stop_words = {'a', 'the'}
filtered_words = [] for word in words: if word not in stop_words: filtered_words.append(word) print(filtered_words)
# ['hi', 'hello', 'Python']
</pre>
<p>You first create a list of words to be filtered and stored in an initially empty list <code>filtered_words</code>. Second, you create a <a href="https://blog.finxter.com/sets-in-python/" title="The Ultimate Guide to Python Sets – with Harry Potter Examples">set </a>of stop words against you want to check the words in the list. Note that it’s far more efficient to use the set data structure for this because <a href="https://blog.finxter.com/complexity-of-python-operations/" target="_blank" rel="noreferrer noopener" title="Complexity of Python Operations">checking membership in sets is much faster </a>than checking membership in lists. <a href="https://blog.finxter.com/sets-in-python/" target="_blank" rel="noreferrer noopener" title="The Ultimate Guide to Python Sets – with Harry Potter Examples">See this tutorial for a full guide on Python sets.</a></p>
<p>You now iterate over all elements in the list <code>words</code> and add them to the <code>filtered_words</code> list if they are not in the set <code>stop_words</code>. </p>
<p><strong>Solution</strong>: You can one-linerize this filtering process using the following code:</p>
<pre class="EnlighterJSRAW" data-enlighter-language="generic" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">filtered_words = [word for word in words if word not in stop_words]</pre>
<p>The solution uses <a href="https://blog.finxter.com/list-comprehension/" title="List Comprehension in Python — A Helpful Illustrated Guide">list comprehension</a> to, essentially, create a <a href="https://blog.finxter.com/python-one-line-for-loop-a-simple-tutorial/" title="Python One Line For Loop [A Simple Tutorial]">single-line for loop</a>. </p>
<p>Here’s the complete code that solves the problem using the one-liner filtering method:</p>
<pre class="EnlighterJSRAW" data-enlighter-language="generic" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group=""># FINXTER TUTORIAL:
# How to filter a list of words? words = ['hi', 'hello', 'Python', 'a', 'the']
stop_words = {'a', 'the'}
filtered_words = [word for word in words if word not in stop_words] print(filtered_words)
# ['hi', 'hello', 'Python']</pre>
<p>Here’s a short tutorial on filtering in case you need more explanations:</p>
<p><strong>Related Article</strong>:<a href="https://blog.finxter.com/how-to-filter-a-list-in-python/" target="_blank" rel="noreferrer noopener" title="How to Filter a List in Python?"> How to Filter a List in Python?</a></p>
<h2>Python One Line If Append</h2>
<p>In the previous example, you’ve already seen how to use the if statement in the list comprehension statement to append more elements to a list if they full-fill a given condition. </p>
<p>How can you filter a list in Python using an arbitrary condition? The most Pythonic and most performant way is to use list comprehension <code>[x for x in list if condition]</code> to filter all elements from a list. </p>
<figure class="wp-block-embed-youtube wp-block-embed is-type-video is-provider-youtube wp-embed-aspect-16-9 wp-has-aspect-ratio">
<div class="wp-block-embed__wrapper">
<div class="ast-oembed-container"><iframe title="How to Filter a List in Python?" width="1400" height="788" src="https://www.youtube.com/embed/3nG4TLkqzf8?feature=oembed" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe></div>
</div>
</figure>
<p><strong>Try It Yourself:</strong></p>
<p> <iframe src="https://repl.it/@finxter/filterlistpython?lite=true" scrolling="no" allowtransparency="true" allowfullscreen="true" sandbox="allow-forms allow-pointer-lock allow-popups allow-same-origin allow-scripts allow-modals" width="100%" height="400px" frameborder="no"></iframe> </p>
<p>The most Pythonic way of filtering a list—in my opinion—is the list comprehension statement <code>[x for x in list if condition]</code>. You can replace condition with any function of <code>x</code> you would like to use as a filtering condition. </p>
<p>For example, if you want to filter all elements that are smaller than, say, 10, you’d use the list comprehension statement <code>[x for x in list if x<10]</code> to create a new list with all list elements that are smaller than 10. </p>
<p>Here are three examples of filtering a list:</p>
<ul>
<li>Get elements smaller than eight: <code>[x for x in lst if x<8]</code>.</li>
<li>Get even elements: <code>[x for x in lst if x%2==0]</code>.</li>
<li>Get odd elements: <code>[x for x in lst if x%2]</code>.</li>
</ul>
<pre class="EnlighterJSRAW" data-enlighter-language="generic" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">lst = [8, 2, 6, 4, 3, 1] # Filter all elements <8
small = [x for x in lst if x<8]
print(small) # Filter all even elements
even = [x for x in lst if x%2==0]
print(even) # Filter all odd elements
odd = [x for x in lst if x%2]
print(odd)</pre>
<p>The output is:</p>
<pre class="EnlighterJSRAW" data-enlighter-language="generic" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group=""># Elements <8
[2, 6, 4, 3, 1] # Even Elements
[8, 2, 6, 4] # Odd Elements
[3, 1]</pre>
<p>This is the most efficient way of filtering a list and it’s also the most Pythonic one. If you look for alternatives though, keep reading because I’ll explain to you each and every nuance of filtering lists in Python in this comprehensive guide.</p>
<h2>Python Append One Line to File</h2>
<figure class="wp-block-embed-youtube wp-block-embed is-type-video is-provider-youtube wp-embed-aspect-16-9 wp-has-aspect-ratio">
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<div class="ast-oembed-container"><iframe title="Python One-Liner: Write String to File" width="1400" height="788" src="https://www.youtube.com/embed/Kv7mdHFfiNM?feature=oembed" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe></div>
</div>
</figure>
<p><strong>Problem</strong>: Given a string and a filename. How to write the string into the file with filename using only a <a href="https://pythononeliners.com/" target="_blank" rel="noreferrer noopener" title="https://pythononeliners.com/">single line of Python code</a>?</p>
<p><strong>Example</strong>: You have filename <code>'hello.txt'</code> and you want to write string <code>'hello world!'</code> into the file.</p>
<pre class="EnlighterJSRAW" data-enlighter-language="generic" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">hi = 'hello world!'
file = 'hello.txt' # Write hi in file '''
# File: 'hello.txt':
hello world! '''</pre>
<p>How to achieve this? In this tutorial, you’ll learn four ways of doing it in a single line of code!</p>
<p>Here’s a quick overview in our interactive <a href="https://blog.finxter.com/how-to-embed-a-python-interpreter-in-your-website/" target="_blank" rel="noreferrer noopener" title="How to Embed a Python Interpreter in Your Website?">Python shell</a>:</p>
<p> <iframe src="https://repl.it/@finxter/writefilesingleline?lite=true" scrolling="no" allowtransparency="true" allowfullscreen="true" sandbox="allow-forms allow-pointer-lock allow-popups allow-same-origin allow-scripts allow-modals" width="100%" height="900px" frameborder="no"></iframe> </p>
<p><em><strong>Exercise</strong>: Run the code and check the file <code>'hello.txt'</code>. How many <code>'hello worlds!'</code> are there in the file? Change the code so that only one <code>'hello world!'</code> is in the file!</em></p>
<p>The most straightforward way is to use the <code><a href="https://docs.python.org/3/reference/compound_stmts.html#the-with-statement" target="_blank" rel="noreferrer noopener" title="https://docs.python.org/3/reference/compound_stmts.html#the-with-statement">with</a></code> statement in a single line (without line break). </p>
<pre class="EnlighterJSRAW" data-enlighter-language="generic" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">hi = 'hello world!'
file = 'hello.txt' # Method 1: 'with' statement
with open(file, 'a') as f: f.write(hi) '''
# File: 'hello.txt':
hello world! '''</pre>
<p>You use the following steps:</p>
<ul>
<li>The <code>with</code> environment makes sure that there are no side-effects such as open files.</li>
<li>The <code>open(file, 'a')</code> statement opens the file with filename <code>file</code> and <a href="https://blog.finxter.com/python-list-append/" target="_blank" rel="noreferrer noopener" title="Python List append() Method">appends </a>the text you write to the contents of the file. You can also use <code>open(file, <strong>'w'</strong>)</code> to overwrite the existing file content.</li>
<li>The new file returned by the <code>open()</code> statement is named <code>f</code>.</li>
<li>In the <code>with</code> body, you use the statement <code>f.write(string)</code> to write <code>string</code> into the file <code>f</code>. In our example, the string is <code>'hello world!'</code>. </li>
</ul>
<p>Of course, a prettier way to write this in two lines would be to use proper <a href="https://blog.finxter.com/pep-8-hanging-indentation-and-closing-brackets-in-python/" target="_blank" rel="noreferrer noopener" title="PEP 8: Hanging Indentation and Closing Brackets in Python">indentation</a>:</p>
<pre class="EnlighterJSRAW" data-enlighter-language="generic" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">with open(file, 'a') as f: f.write(hi)</pre>
<p>This is the most well-known way to write a string into a file. The big advantage is that you don’t have to close the file—the <code>with</code> environment does it for you! That’s why many coders consider this to be the most <a href="https://blog.finxter.com/python-crash-course/" target="_blank" rel="noreferrer noopener" title="Python Programming Tutorial [+Cheat Sheets]">Pythonic </a>way.</p>
<p>You can find more ways on my detailed blog article.</p>
<p><strong>Related Article:</strong> <a href="https://blog.finxter.com/python-one-liner-write-string-to-file/" target="_blank" rel="noreferrer noopener" title="Python One-Liner: Write String to File">Python One-Liner: Write String to File</a></p>
<h2>Python One-Liners Book</h2>
<p><strong>Python programmers will improve their computer science skills with these useful one-liners.</strong></p>
<figure class="wp-block-image size-medium is-resized"><a href="https://www.amazon.com/gp/product/B07ZY7XMX8" target="_blank" rel="noopener noreferrer"><img src="https://blog.finxter.com/wp-content/uploads/2020/06/3D_cover-1024x944.jpg" alt="Python One-Liners" class="wp-image-10007" width="512" height="472" srcset="https://blog.finxter.com/wp-content/uploads/2020/06/3D_cover-scaled.jpg 1024w, https://blog.finxter.com/wp-content/uplo...00x277.jpg 300w, https://blog.finxter.com/wp-content/uplo...68x708.jpg 768w" sizes="(max-width: 512px) 100vw, 512px" /></a></figure>
<p><a href="https://amzn.to/2WAYeJE" target="_blank" rel="noreferrer noopener" title="https://amzn.to/2WAYeJE"><em>Python One-Liners</em> </a>will teach you how to read and write “one-liners”: concise statements of useful functionality packed into a single line of code. You’ll learn how to systematically unpack and understand any line of Python code, and write eloquent, powerfully compressed Python like an expert.</p>
<p>The book’s five chapters cover tips and tricks, regular expressions, machine learning, core data science topics, and useful algorithms. Detailed explanations of one-liners introduce key computer science concepts and boost your coding and analytical skills. You’ll learn about advanced Python features such as list comprehension, slicing, lambda functions, regular expressions, map and reduce functions, and slice assignments. You’ll also learn how to:</p>
<p><strong>•</strong> Leverage data structures to solve real-world problems, like using Boolean indexing to find cities with above-average pollution<br /><strong>•</strong> Use NumPy basics such as array, shape, axis, type, broadcasting, advanced indexing, slicing, sorting, searching, aggregating, and statistics<br /><strong>•</strong> Calculate basic statistics of multidimensional data arrays and the K-Means algorithms for unsupervised learning<br /><strong>•</strong> Create more advanced regular expressions using grouping and named groups, negative lookaheads, escaped characters, whitespaces, character sets (and negative characters sets), and greedy/nongreedy operators<br /><strong>•</strong> Understand a wide range of computer science topics, including anagrams, palindromes, supersets, permutations, factorials, prime numbers, Fibonacci numbers, obfuscation, searching, and algorithmic sorting</p>
<p>By the end of the book, you’ll know how to write Python at its most refined, and create concise, beautiful pieces of “Python art” in merely a single line.</p>
<p><strong><a href="https://amzn.to/2WAYeJE" target="_blank" rel="noreferrer noopener" title="https://amzn.to/2WAYeJE"><em>Get your Python One-Liners Now!!</em></a></strong></p>
</div>
https://www.sickgaming.net/blog/2020/08/...ne-append/