Python function syntax

Language Help Python
1

Hey guys I have one question. When can I print functinos in python without print() and when I must include print(functions inside)? Like in code bellow. First set of code prints function but second doesn’t. I do not understand why. Sometimes I can print functions just by typing functions name with brackets.

And one more thing. When printing function the actual printing doesn’t calculate the function but actually looks for return value? Could that be a reason why when you omit the return from the function the print value is ‘None’ ? Just curious how does it actually work in the background.
‘’
current_year = 2048
def calculate_age(birth_year):
age = current_year - birth_year
return age

print(calculate_age(1970))

current_year = 2048
def calculate_age(birth_year):
age = current_year - birth_year
return age

calculate_age(1970)
‘’

Thank you for answear and your time.

2

You can call functions in python without using print() when your function has a print() statement inside of it.
Example:

def my_function():
  print(4)
my_function()#outputs 4

In the example above you called my_function by doing my_function(), and that calls (returns basically) anything inside of my_function. There is a print statement inside of my_function, so that is why it will output (or print) 4 when called.
However, you must call my_function without printing the results, because a function without a return statement automatically returns None. If you were to print my_function, you would get an output of 4 and None.
Alternatively, you can look at it like this:

def my_function():
  print(4)
  return None #if you don't have a return statement, this is automatically added to your function when it is called
my_function() #outputs 4
print(my_function()) #outputs 4 and None

You must print your function whenever you have a return statement inside of it. (That’s assuming you want to see your function results).
Example:

def my_function():
  return 4
print(my_function())#outputs 4

You cannot see the results of a return statement simply by calling it. You must print the result.

def my_function():
  return 4
  print(6)
my_function()#outputs 6 but not 4

current_year = 2048
def calculate_age(birth_year):
age = current_year - birth_year
return age

print(calculate_age(1970))

Same thing here. You must print a function to see the results of return age.

current_year = 2048
def calculate_age(birth_year):
age = current_year - birth_year
return age

calculate_age(1970)#doesn't output anything

Now, just because you cannot see the results of a return statement doesn’t mean the result wasn’t returned.
Example:

def my_function():
  return 4
my_function()#will return 4 so I can save this to a variable and print that variable.
my_function_results = my_function()
print(my_function_results)#will output 4

Case in point. But you must still no matter what print a function with a return statement to see the results.

All printing a function does is print EVERYTHING inside of it. That’s why when you print a function without a return statement, the added return None is printed as well.
As I made a bad joke about this:
What does a function return when it doesn’t return anything?
None-thing!

Ooh one more thing if you didn’t already know this! WHENEVER you try to call or print a function to get its results, you must write it like this:

my_function()#the parenthesis is what allows the results to be called.
print(my_function)#will give you something like <function object at #&*^$#>

Hope this helps!

3

Thank you. I get it now.

If I want just to print print() statement from the function I use function(). But if I want also actual result stored in function I use print(function()). That you wanted to say if I am corrent?

4

Whether you print, or just call a function, you will get the results. The form you get them in however, depends on what is in the function and whether you print it or call it.

def my_function():
  print(5)

my_function()#5
print(my_function())#5 None

def function1():
  return 5

function1()#will not print out anything but this call returns 5
print(function1())#5
5

Got it.

To have things clear printing function means this: print(function())?
And calling function means this: function()?

Or around?

1 Like
6

You’re right! Well, more like printing the function call. But yeah. I’m glad I was able to help! :smile: