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[Tut] Convert CSV to List of Tuples in Python

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Convert CSV to List of Tuples in Python

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<div class="kksr-legend"> 4.5/5 – (2 votes) </div>
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<figure class="aligncenter size-large"><img loading="lazy" width="1024" height="576" src="https://blog.finxter.com/wp-content/uploads/2022/06/python_csv_to_list_of_tuples-1024x576.jpg" alt="Convert CSV to List of Tuples in Python" class="wp-image-435167" srcset="https://blog.finxter.com/wp-content/uploads/2022/06/python_csv_to_list_of_tuples-1024x576.jpg 1024w, https://blog.finxter.com/wp-content/uplo...00x169.jpg 300w, https://blog.finxter.com/wp-content/uplo...68x432.jpg 768w, https://blog.finxter.com/wp-content/uplo...tuples.jpg 1280w" sizes="(max-width: 1024px) 100vw, 1024px" /></figure>
</div>
<h2>Problem Formulation</h2>
<p>Given a CSV file (e.g., stored in the file with name <code>'my_file.csv'</code>). </p>
<pre class="wp-block-preformatted"><code><strong>INPUT</strong>: file 'my_file.csv'</code>
<code>9,8,7
6,5,4
3,2,1</code></pre>
<p><strong>Challenge</strong>: How to convert the CSV file to a list of tuples, i.e., putting the row values into the inner <a href="https://blog.finxter.com/the-ultimate-guide-to-python-tuples/" data-type="post" data-id="12043" target="_blank" rel="noreferrer noopener">tuples</a>?</p>
<pre class="wp-block-preformatted"><code><strong>OUTPUT</strong>: Python list of tuples</code>
<code>[(9, 8, 7), (6, 5, 4), (3, 2, 1)]</code></pre>
<h2>Method 1: csv.reader()</h2>
<div class="wp-block-cover aligncenter"><span aria-hidden="true" class="wp-block-cover__background has-background-dim-80 has-background-dim"></span><img loading="lazy" width="642" height="642" class="wp-block-cover__image-background wp-image-426802" alt="" src="https://blog.finxter.com/wp-content/uploads/2022/06/finxter_square.png" data-object-fit="cover" srcset="https://blog.finxter.com/wp-content/uploads/2022/06/finxter_square.png 642w, https://blog.finxter.com/wp-content/uplo...00x300.png 300w, https://blog.finxter.com/wp-content/uplo...50x150.png 150w" sizes="(max-width: 642px) 100vw, 642px" /></p>
<div class="wp-block-cover__inner-container">
<p class="has-text-align-center has-base-3-color has-text-color has-x-large-font-size"><strong>Method 1: csv.reader()</strong></p>
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</div>
<p class="has-global-color-8-background-color has-background">To convert a CSV file <code>'my_file.csv'</code> into a list of tuples in Python, use <code>csv.reader(file_obj)</code> to create a CSV file reader that holds an iterable of lists, one per row. Now, use the <a rel="noreferrer noopener" href="https://blog.finxter.com/python-list/" data-type="URL" data-id="https://blog.finxter.com/python-list/" target="_blank"><code>list(tuple(line) for line in reader)</code></a> expression with a <a rel="noreferrer noopener" href="https://blog.finxter.com/understanding-generators-in-python/" data-type="post" data-id="33873" target="_blank">generator expression</a> to convert each inner list to a tuple.</p>
<p>Here’s a simple example that converts our CSV file to a nested list using this approach:</p>
<pre class="EnlighterJSRAW" data-enlighter-language="python" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">import csv csv_filename = 'my_file.csv' with open(csv_filename) as f: reader = csv.reader(f) lst = list(tuple(line) for line in reader)</pre>
<p>Output:</p>
<pre class="EnlighterJSRAW" data-enlighter-language="python" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">print(lst)
# [('9', '8', '7'), ('6', '5', '4'), ('3', '2', '1')]</pre>
<h2>Method 2: One-Liner</h2>
<div class="wp-block-cover aligncenter"><span aria-hidden="true" class="wp-block-cover__background has-background-dim-80 has-background-dim"></span><img loading="lazy" width="642" height="642" class="wp-block-cover__image-background wp-image-426802" alt="" src="https://blog.finxter.com/wp-content/uploads/2022/06/finxter_square.png" data-object-fit="cover" srcset="https://blog.finxter.com/wp-content/uploads/2022/06/finxter_square.png 642w, https://blog.finxter.com/wp-content/uplo...00x300.png 300w, https://blog.finxter.com/wp-content/uplo...50x150.png 150w" sizes="(max-width: 642px) 100vw, 642px" /></p>
<div class="wp-block-cover__inner-container">
<p class="has-text-align-center has-base-3-color has-text-color has-x-large-font-size"><strong>Method 2: One-Liner</strong></p>
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</div>
<p class="has-base-3-background-color has-background">You can also convert a CSV to a list of tuples using the following <a rel="noreferrer noopener" href="https://pythononeliners.com/" data-type="URL" data-id="https://pythononeliners.com/" target="_blank">Python one-liner</a> idea:</p>
<p class="has-global-color-8-background-color has-background">Open the file using <code><a rel="noreferrer noopener" href="https://blog.finxter.com/python-open-function/" data-type="post" data-id="24793" target="_blank">open()</a></code>, pass the file object into <code><a rel="noreferrer noopener" href="https://blog.finxter.com/how-to-read-a-csv-file-into-a-python-list/" data-type="post" data-id="8185" target="_blank">csv.reader()</a></code>, and convert the CSV reader object to a list using the <code><a rel="noreferrer noopener" href="https://blog.finxter.com/python-list/" data-type="post" data-id="21502" target="_blank">list()</a></code> built-in function in Python with a <a href="https://blog.finxter.com/python-one-line-generator/" data-type="post" data-id="13194" target="_blank" rel="noreferrer noopener">generator expression</a> to convert each inner list to a tuple.</p>
<p>Here’s how that looks:</p>
<pre class="EnlighterJSRAW" data-enlighter-language="python" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">import csv; lst=list(tuple(line) for line in csv.reader(open('my_file.csv'))); print(lst)</pre>
<p>Concise, isn’t it? <img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f642.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" /></p>
<p>The output is the same:</p>
<pre class="wp-block-preformatted"><code>[('9', '8', '7'), ('6', '5', '4'), ('3', '2', '1')]</code></pre>
<p>By the way: <em>Do you need all inner elements converted to a certain data type such as integer?</em></p>
<p>If so, use the following approach on top of the previously shown list <code>lst</code>:</p>
<pre class="EnlighterJSRAW" data-enlighter-language="python" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">new_lst = [tuple(int(x) for x in inner) for inner in lst]</pre>
<p>The converted <code>new_lst</code> now contains a list of tuples of ints:</p>
<pre class="EnlighterJSRAW" data-enlighter-language="python" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">print(new_lst)
# [('9', '8', '7'), ('6', '5', '4'), ('3', '2', '1')]</pre>
<h2>Method 3: Pandas</h2>
<div class="wp-block-cover aligncenter"><span aria-hidden="true" class="wp-block-cover__background has-background-dim-80 has-background-dim"></span><img loading="lazy" width="642" height="642" class="wp-block-cover__image-background wp-image-426802" alt="" src="https://blog.finxter.com/wp-content/uploads/2022/06/finxter_square.png" data-object-fit="cover" srcset="https://blog.finxter.com/wp-content/uploads/2022/06/finxter_square.png 642w, https://blog.finxter.com/wp-content/uplo...00x300.png 300w, https://blog.finxter.com/wp-content/uplo...50x150.png 150w" sizes="(max-width: 642px) 100vw, 642px" /></p>
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<p class="has-text-align-center has-base-3-color has-text-color has-x-large-font-size"><strong>Method 3: Pandas</strong></p>
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</div>
<p class="has-global-color-8-background-color has-background">You can convert a CSV to a list of tuples with Pandas by first <a href="https://blog.finxter.com/read-and-write-flat-files-with-pandas/" data-type="post" data-id="62847">readin</a><a rel="noreferrer noopener" href="https://blog.finxter.com/read-and-write-flat-files-with-pandas/" data-type="post" data-id="62847" target="_blank">g</a><a href="https://blog.finxter.com/read-and-write-flat-files-with-pandas/" data-type="post" data-id="62847"> the CSV</a> without header line using <code>pd.read_csv('my_file.csv', header=None)</code> function and second converting the resulting DataFrame to a nested list using <code><a rel="noreferrer noopener" href="https://blog.finxter.com/dataframe-to-a-list-and-vice-versa/" data-type="post" data-id="111548" target="_blank">df.values.tolist()</a></code>. Third, <a href="https://blog.finxter.com/how-to-convert-list-of-lists-to-list-of-tuples-in-python/" data-type="post" data-id="7953" target="_blank" rel="noreferrer noopener">convert</a> the nested list to a list of tuples and you’re done.</p>
<p>Here’s an example that converts the CSV to a Pandas DataFrame and then to a nested raw Python list and then to a list of tuples:</p>
<pre class="EnlighterJSRAW" data-enlighter-language="python" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">import pandas as pd # CSV to DataFrame
df = pd.read_csv('my_file.csv', header=None) # DataFrame to List of Lists
lst = df.values.tolist() # List of Lists to List of Tuples:
new_lst = [tuple(x) for x in lst] print(new_lst)
# [(9, 8, 7), (6, 5, 4), (3, 2, 1)]</pre>
<p>This was easy, wasn’t it? <img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f642.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" /></p>
<p>Of course, you can also one-linerize it by chaining commands like so:</p>
<pre class="EnlighterJSRAW" data-enlighter-language="python" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group=""># One-Liner to convert CSV to list of tuples:
lst = [tuple(x) for x in pd.read_csv('my_file.csv', header=None).values.tolist()]</pre>
<h2>Method 4: Raw Python No Dependency</h2>
<div class="wp-block-cover aligncenter"><span aria-hidden="true" class="wp-block-cover__background has-background-dim-80 has-background-dim"></span><img loading="lazy" width="642" height="642" class="wp-block-cover__image-background wp-image-426802" alt="" src="https://blog.finxter.com/wp-content/uploads/2022/06/finxter_square.png" data-object-fit="cover" srcset="https://blog.finxter.com/wp-content/uploads/2022/06/finxter_square.png 642w, https://blog.finxter.com/wp-content/uplo...00x300.png 300w, https://blog.finxter.com/wp-content/uplo...50x150.png 150w" sizes="(max-width: 642px) 100vw, 642px" /></p>
<div class="wp-block-cover__inner-container">
<p class="has-text-align-center has-base-3-color has-text-color has-x-large-font-size"><strong>Method 4: Raw Python No Dependency</strong></p>
</div>
</div>
<p>If you’re like me, you try to avoid using dependencies if they are not needed. Raw Python is often more efficient and simple enough anyways. Also, you don’t open yourself up to unnecessary risks and complexities.</p>
<p class="has-base-background-color has-background"><strong>Question</strong>: So, is there a simple way to read a CSV to a list of tuples in raw Python without external dependencies? </p>
<p>Sure!</p>
<p class="has-global-color-8-background-color has-background">To read a CSV to a list of tuples in pure Python, open the file using <code><a rel="noreferrer noopener" href="https://blog.finxter.com/python-open-function/" data-type="post" data-id="24793" target="_blank">open('my_file.csv')</a></code>, read all lines into a variable using <code><a rel="noreferrer noopener" href="https://blog.finxter.com/how-to-read-first-n-lines-of-a-file-in-python/" data-type="post" data-id="30520" target="_blank">f.readlines()</a></code>. Iterate over all lines, strip them from whitespace using <code><a rel="noreferrer noopener" href="https://blog.finxter.com/python-string-strip/" data-type="post" data-id="26104" target="_blank">strip()</a></code>, split them on the delimiter <code>','</code> using <code><a rel="noreferrer noopener" href="https://blog.finxter.com/python-string-split/" data-type="post" data-id="26097" target="_blank">split(',')</a></code>, and pass everything in the <code><a href="https://blog.finxter.com/python-tuple/" data-type="post" data-id="21575" target="_blank" rel="noreferrer noopener">tuple()</a></code> function.</p>
<p>You can accomplish this in a simple <a href="https://blog.finxter.com/list-comprehension/" data-type="post" data-id="1171" target="_blank" rel="noreferrer noopener">list comprehension</a> statement like so:</p>
<pre class="EnlighterJSRAW" data-enlighter-language="python" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">csv_filename = 'my_file.csv' with open(csv_filename) as f: lines = f.readlines() lst = [tuple(line.strip().split(',')) for line in lines] print(lst)</pre>
<p>Feel free to check out my detailed video in case you need a refresher on the powerful Python concept list comprehension:</p>
<figure class="wp-block-embed is-type-video is-provider-youtube wp-block-embed-youtube wp-embed-aspect-16-9 wp-has-aspect-ratio">
<div class="wp-block-embed__wrapper">
<iframe loading="lazy" title="A Simple Introduction to List Comprehension in Python" width="780" height="439" src="https://www.youtube.com/embed/9qsq2Vf48W8?feature=oembed" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>
</div>
</figure>
<p class="has-base-background-color has-background"><img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f30d.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" /> <strong>Related Tutorial</strong>: <a href="https://blog.finxter.com/list-comprehension/" data-type="post" data-id="1171" target="_blank" rel="noreferrer noopener">Understanding List Comprehension in Python</a>.</p>
<div class="wp-block-cover aligncenter"><span aria-hidden="true" class="wp-block-cover__background has-background-dim-80 has-background-dim"></span><img loading="lazy" width="642" height="642" class="wp-block-cover__image-background wp-image-426802" alt="" src="https://blog.finxter.com/wp-content/uploads/2022/06/finxter_square.png" data-object-fit="cover" srcset="https://blog.finxter.com/wp-content/uploads/2022/06/finxter_square.png 642w, https://blog.finxter.com/wp-content/uplo...00x300.png 300w, https://blog.finxter.com/wp-content/uplo...50x150.png 150w" sizes="(max-width: 642px) 100vw, 642px" /></p>
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<p class="has-text-align-center has-base-3-color has-text-color has-x-large-font-size"><strong>Become a One-Liner Wizard!</strong></p>
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</div>
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<figure class="aligncenter size-medium is-resized"><a href="https://www.amazon.com/gp/product/B07ZY7XMX8" target="_blank" rel="noopener noreferrer"><img loading="lazy" 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>
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