Do you need to create a function that returns a string but you don’t know how? No worries, in sixty seconds, you’ll know! Go!

A Python function can return any object such as a string. To return a string, create the string object within the function body, assign it to a variable my_string, and return it to the caller of the function using the keyword operation return my_string. Or simply create the string within the return expression like so: return "hello world"

def f(): return 'hello world' f()

# hello world

Create String in Function Body

Let’s have a look at another example:

The following code creates a function create_string() that iterates over all numbers 0, 1, 2, …, 9, appends them to the string my_string, and returns the string to the caller of the function:

def create_string(): ''' Function to return string ''' my_string = '' for i in range(10): my_string += str(i) return my_string s = create_string()

print(s)

# 0123456789

Note that you store the resulting string in the variable s. The local variable my_string that you created within the function body is only visible within the function but not outside of it.

So, if you try to access the name my_string, Python will raise a NameError:

>>> print(my_string)

Traceback (most recent call last): File "<pyshell#1>", line 1, in <module> print(my_string)

NameError: name 'my_string' is not defined

To fix this, simply assign the return value of the function — a string — to a new variable and access the content of this new variable:

>>> s = create_string()

>>> print(s)

0123456789

There are many other ways to return a string in Python.

Return String With List Comprehension

For example, you can use a list comprehension in combination with the string.join() method instead that is much more concise than the previous code—but creates the same string of digits:

def create_string(): ''' Function to return string ''' return ''.join([str(i) for i in range(10)]) s = create_string()

print(s)

# 0123456789

For a quick recap on list comprehension, feel free to scroll down to the end of this article.

You can also add some separator strings like so:

def create_string(): ''' Function to return string ''' return ' xxx '.join([str(i) for i in range(10)]) s = create_string()

print(s)

# 0 xxx 1 xxx 2 xxx 3 xxx 4 xxx 5 xxx 6 xxx 7 xxx 8 xxx 9

Return String with String Concatenation

You can also use a string concatenation and string multiplication statement to create a string dynamically and return it from a function.

Here’s an example of string multiplication:

def create_string(): ''' Function to return string ''' return 'ho' * 10 s = create_string()

print(s)

# hohohohohohohohohoho

String Concatenation of Function Arguments

Here’s an example of string concatenation that appends all arguments to a given string and returns the result from the function:

def create_string(a, b, c): ''' Function to return string ''' return 'My String: ' + a + b + c s = create_string('python ', 'is ', 'great')

print(s)

# My String: python is great

Concatenate Arbitrary String Arguments and Return String Result

You can also use dynamic argument lists to be able to add an arbitrary number of string arguments and concatenate all of them:

def create_string(*args): ''' Function to return string ''' return ' '.join(str(x) for x in args) print(create_string('python', 'is', 'great'))

# python is great print(create_string(42, 41, 40, 41, 42, 9999, 'hi'))

# 42 41 40 41 42 9999 hi

Background List Comprehension

Knowledge: List comprehension is a very useful Python feature that allows you to dynamically create a list by using the syntax [expression context]. You iterate over all elements in a given context “for i in range(10)“, and apply a certain expression, e.g., the identity expression i, before adding the resulting values to the newly-created list.

In case you need to learn more about list comprehension, feel free to check out my explainer video:

Programmer Humor

Q: How do you tell an introverted computer scientist from an extroverted computer scientist? A: An extroverted computer scientist looks at your shoes when he talks to you.

Most of the APIs are used to accept requests and send responses in JSON format. JSON is the de-facto data exchange format. It is important to learn how to send JSON request data with an API call.

The cURL is a way of remote accessing the API endpoint over the network. The below code will save you time to achieve posting JSON data via PHP cURL.

Example: PHP cURL POST by Sending JSON Data

It prepares the JSON from an input array and bundles it to the PHP cURL post.

It uses PHP json_encode function to get the encoded request parameters. Then, it uses the CURLOPT_POSTFIELDS option to bundle the JSON data to be posted.

curl-post-json.php

<?php

// URL of the API that is to be invoked and data POSTed

$url = 'https://example.com/api-to-post'; // request data that is going to be sent as POST to API

$data = array( "animal" => "Lion", "type" => "Wild", "name" => "Simba", "zoo" => array( "address1" => "5333 Zoo", "city" => "Los Angeles", "state" => "CA", "country" => "USA", "zipcode" => "90027" )

); // encoding the request data as JSON which will be sent in POST

$encodedData = json_encode($data); // initiate curl with the url to send request

$curl = curl_init($url); // return CURL response

curl_setopt($curl, CURLOPT_RETURNTRANSFER, true); // Send request data using POST method

curl_setopt($curl, CURLOPT_CUSTOMREQUEST, "POST"); // Data conent-type is sent as JSON

curl_setopt($curl, CURLOPT_HTTPHEADER, array( 'Content-Type:application/json'

));

curl_setopt($curl, CURLOPT_POST, true); // Curl POST the JSON data to send the request

curl_setopt($curl, CURLOPT_POSTFIELDS, $encodedData); // execute the curl POST request and send data

$result = curl_exec($curl);

curl_close($curl); // if required print the curl response

print $result;

?>

The above code is one part of the API request-response cycle. If the endpoint belongs to some third-party API, this code is enough to complete this example.

But, if the API is in the intra-system (custom API created for the application itself), then, the posted data has to be handled.

How to get the JSON data in the endpoint

This is to handle the JSON data posted via PHP cURL in the API endpoint.

It used json_decode to convert the JSON string posted into a JSON object. In this program, it sets “true” to convert the request data into an array.

curl-request-data.php

<?php

// use the following code snippet to receive

// JSON POST data

// json_decode converts the JSON string to JSON object

$data = json_decode(file_get_contents('php://input'), true);

print_r($data);

echo $data;

?>

The json_encode function also allows setting the allowed nesting limit of the input JSON. The default limit is 512.

If the posted JSON data is exceeding the nesting limit, then the API endpoint will be failed to get the post data.

Other modes of posting data to a cURL request

In a previous tutorial, we have seen many examples of sending requests with PHP cURL POST.

This program sets the content type “application/json” in the CURLOPT_HTTPHEADER. There are other modes of posting data via PHP cURL.

1. multipart/form-data – to send an array of post data to the endpoint/
2. application/x-www-form-urlencoded – to send a URL-encoded string of form data.

Note: PHP http_build_query() can output the URL encoded string of an array.
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