Python doctests: test for None

Python doctests: test for None

You can write doctests in Python to test functions that return None. To do this, you can include an expected None value in your function's docstring and use the >>> prompt to indicate the function call. Here's an example:

def my_function(arg): """ This function does something and returns None. Parameters: arg (int): An integer argument. Returns: None Examples: >>> my_function(5) None >>> my_function(0) None """ # Your function logic here return None

In this example, my_function takes an integer argument and returns None. The doctests demonstrate how to call the function with different arguments and verify that the return value is indeed None.

To run the doctests, you can use the doctest module by adding the following code at the bottom of your Python script:

if __name__ == "__main__": import doctest doctest.testmod()

When you run your script, the doctest module will execute the examples in your docstrings, including the ones testing for None, and report any failures or errors.

Examples

    def divide(a, b): """ Divides two numbers. >>> divide(6, 2) 3.0 >>> divide(0, 5) 0.0 >>> divide(5, 0) """ if b == 0: return None else: return a / b 
      def find_index(lst, item): """ Finds the index of an item in a list. >>> find_index([1, 2, 3], 2) 1 >>> find_index(['a', 'b', 'c'], 'd') """ if item in lst: return lst.index(item) else: return None 
        def process_data(data): """ Processes input data. >>> process_data([1, 2, 3]) 'Data processed successfully.' >>> process_data([]) """ if data: # Process data here return 'Data processed successfully.' else: return None 
          def fetch_data(url): """ Fetches data from a URL. >>> fetch_data("https://example.com/data") 'Data retrieved successfully.' >>> fetch_data("https://nonexistenturl.com") """ # Fetch data from the URL if url == "https://example.com/data": return 'Data retrieved successfully.' else: return None 
            def process_input(user_input): """ Processes user input. >>> process_input("yes") True >>> process_input("no") False >>> process_input("") """ if user_input.lower() == "yes": return True elif user_input.lower() == "no": return False else: return None 
              def validate_email(email): """ Validates an email address. >>> validate_email("example@example.com") True >>> validate_email("notanemail") False >>> validate_email("") """ # Validate the email address if "@" in email and "." in email: return True else: return None 
                def search_item(lst, item): """ Searches for an item in a list. >>> search_item([1, 2, 3], 2) True >>> search_item(['a', 'b', 'c'], 'd') False >>> search_item([], 'item') """ if item in lst: return True else: return None 
                  def square_root(num): """ Calculates the square root of a number. >>> square_root(9) 3.0 >>> square_root(-4) """ if num >= 0: return num ** 0.5 else: return None 
                    def check_prime(num): """ Checks if a number is prime. >>> check_prime(7) True >>> check_prime(4) False >>> check_prime(1) """ if num <= 1: return None for i in range(2, num): if num % i == 0: return False return True

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