Defining and Calling Functions in Python for Programmers
Python functions are reusable pieces of code that help programmers write programs more efficiently. They are a great tool for organizing and abstracting code, making it easier to read and debug. In Python, functions are defined with the def
keyword, followed by the name of the function and the parameters it takes if any. Functions are called by simply referring to their name and passing the appropriate arguments.
Defining a Function
The syntax for defining a function in Python is:
def function_name(parameters):
"""docstring"""
statement(s)
The keyword def
marks the start of the function definition. The name of the function is function_name
and the parameters are passed as a comma-separated list inside the parentheses. The function's body is indented and the docstring is a description of what the function does. The statement(s) are the instructions that are executed when the function is called.
Examples
Here are some examples of functions to give you a better understanding of how they are defined and called:
Example 1:
The following example is a simple function that takes two numbers as parameters and prints their sum:
def add_numbers(a, b):
"""This function adds two numbers and prints the result"""
print(a + b)
Example 2:
The following example is a function that takes two strings as parameters and returns their concatenation:
def concat_strings(a, b):
"""This function concatenates two strings and returns the result"""
return a + b
Example 3:
The following example is a function that takes a list as a parameter and prints each element in the list:
def print_list(lst):
"""This function prints each element in the list"""
for element in lst:
print(element)
Calling a Function
Once a function is defined, it can be called by referencing its name and passing the appropriate arguments. The syntax for calling a function is:
function_name(arguments)
For example, if we have a function called add_numbers
that takes two numbers as parameters, we can call it like this:
add_numbers(2, 3)
This will print 5
(the sum of 2 and 3).
Tips
- Make sure the function name is descriptive and easy to understand.
- Include a docstring at the beginning of the function to describe what it does.
- Write functions with a single purpose so that they can be reused in different parts of the program.
- Keep functions short; if they are too long, consider breaking them up into smaller functions.
- Use meaningful variable names for parameters and variables inside the function.
- Test your functions thoroughly to make sure they are working as expected.