Print vs Return in Python

First thing to note is that, return and print are statements, not functions.

Basic Explanation

Print only shows the human user a string representing what is going on inside the computer. Though the computer cannot make use of that printing that is why return is a function that gives back a value. With this value it is often unseen by the human user but it can be used by the computer in further functions

Expansive Explanation

Print is like a console.log version of JavaScript. It is mainly for the user to see how it works. It is very useful to understand how a program works and where you can start debugging to check various values in a program without interrupting the program.

return is the main way that helps a function return a value. All functions will return a value, and if there is no return statement (or yield ), it will return None. The value that is returned by a function can then be further used as an argument passed to another function, stored as a variable, or just printed for the benefit of the human user.

Consider these two programs:

def function_prints():
    print "I printed"
def function_returns():
    return "I returned"
f1 = function_prints()
f2 = function_returns()
print "Now let us see what the values of f1 and f2 are"
print f1
print f2

The following is what will be seen in the console:

"I printed"
"Lets see what the values of f1 and f2 are"    
None
"I returned"

When function_prints ran, it automatically printed to the console "I printed". However, the value stored in f1 is None because that function had no return statement.

When function_returns ran, it did not print anything to the console. However, it did return a value, and that value was stored in f2. When we printed f2 at the end of the code, we saw "I returned"

Now let us try another example:

def print_number(num):
    print num
def return_number(num):
    return num
def add_three(num):
    return num + 3
f1 = print_number(7)
f2 = return_number(2)
print f1
print f2
f3 = add_three(f2)
print f3
f4 = add_three(f1)
print f4

In this example, we pass the results of a function to another function. Let us see what the console will say

7
None
2
5
TypeError: unsupported operand type(s) for +: 'NoneType' and 'int'

Notice that we got an error when we tried to pass f1 to add_three because f1 had a value of None, even though it had printed out the correct number. This is why it is important to return values and not print them (except when we want to know what the value is).