Python custom function

Question

I have been working at learning Python over the last week and it has been going really well, however I have now been introduced to custom functions and I sort of hit a wall. While I understand the basics of it, such as:

def helloworld():
    print("Hello World!")

helloworld()

I know this will print "Hello World!".

However, when it comes to getting information from one function to another, I find that confusing. ie: function1 and function2 have to work together to perform a task. Also, when to use the return command.

Lastly, when I have a list or a dictionary inside of a function. I'll make something up just as an example.

def my_function():
    my_dict = {"Key1":Value1,
              "Key2":Value2,
              "Key3":Value3,
              "Key4":Value4,}

How would I access the key/value and be able to change them from outside of the function? ie: If I had a program that let you input/output player stats or a character attributes in a video game.

I understand bits and pieces of this, it just confuses me when they have different functions calling on each other.

Also, since this was my first encounter with the custom functions. Is this really ambitious to pursue and this could be the reason for all of my confusion? Since this is the most complex program I have seen yet.

Answer 1

Functions in python can be both, a regular procedure and a function with a return value. Actually, every Python's function will return a value, which might be None.

If a return statement is not present, then your function will be executed completely and leave normally following the code flow, yielding None as a return value.

def foo():
    pass
foo() == None
>>> True

If you have a return statement inside your function. The return value will be the return value of the expression following it. For example you may have return None and you'll be explicitly returning None. You can also have return without anything else and there you'll be implicitly returning None, or, you can have return 3 and you'll be returning value 3. This may grow in complexity.

def foo():
   print('hello')
   return
   print('world')

foo()
>>>'hello'

def add(a,b):
    return a + b
add(3,4)
>>>7

If you want a dictionary (or any object) you created inside a function, just return it:

def my_function():
    my_dict = {"Key1":Value1,
              "Key2":Value2,
              "Key3":Value3,
              "Key4":Value4,}
    return my_dict
d = my_function()
d['Key1']
>>> Value1

Those are the basics of function calling. There's even more. There are functions that return functions (also treated as decorators. You can even return multiple values (not really, you'll be just returning a tuple) and a lot a fun stuff :)

def two_values():
    return 3,4
a,b = two_values()
print(a)
>>>3
print(b)
>>>4

Hope this helps!