A deep dive into Python functions

In this post I will be discussing Python’s function in depth, accompanied by a bunch of examples on the way to clear up the concepts. All examples are in Python 2.7 but the same concepts should apply to Python 3 with some change in the syntax.

What you need to know about functions

In Python, functions are first class citizens, they are objects and that means we can do a lot of useful stuff with them.

Assign functions to variables

def greet(name):
    return "hello "+name

greet_someone = greet
print greet_someone("John")

# Outputs: hello John

Define functions inside other functions

def greet(name):
    def get_message():
        return "Hello "

    result = get_message()+name
    return result

print greet("John")

# Outputs: Hello John

Functions can be passed as parameters to other functions

def greet(name):
   return "Hello " + name

def call_func(func):
    other_name = "John"
    return func(other_name)

print call_func(greet)

# Outputs: Hello John

Functions can return other functions

In other words, functions generating other functions.

def compose_greet_func():
    def get_message():
        return "Hello there!"

    return get_message

greet = compose_greet_func()
print greet()

# Outputs: Hello there!

Inner functions have access to the enclosing scope

Python only allows read access to the outer scope and not assignment. Notice how we modified the example above to read a “name” argument from the enclosing scope of the inner function and return the new function.

def compose_greet_func(name):
    def get_message():
        return "Hello there "+name+"!"

    return get_message

greet = compose_greet_func("John")
print greet()

# Outputs: Hello there John!

Phew!

That was an introduction and a deep dive to functions in Python. I hope that you found this post helpful, if you have any suggestions or questions please do share their to me and I’ll be sure to get back to you.

Happy coding! :smile: