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bhanubais
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Next: Types

Procedures and functions

Definitions

A procedure is a series of actions that return nothing. A function is a procedure that returns something.

I will imagine like this:

  • If I ask someone to add, it's a procedure, but if I ask for the result, it's a function.

For example, a classic procedure is to print something (print). It doesn't return a result in your code, but it does something. Well, a procedure is when you ask your turtle to do something.

For example, a classic function is precisely the example of addition. We ask to calculate a + b & we want the result.

The reason we write procedures and functions is to be able to cut the code into small pieces. We can suddenly write a function which does a processing so as not to have to repeat the code. If I want to be able to do the following calculation: f (x) = x * x + 55, and I want to calculate the result for 10 different values, it's easier to have a function :).

In python, there are no procedures (not typed). In fact, as I said above, a procedure is a function that returns ** nothing **. In python, nothing has a notation, it is type None.

How can we send something back? The keyword return is there for that. If you don't put it, python will automatically return None.

Take the example of an addition:

def add (a, b):
  c = a + b
  return c

Here we have defined a function, which takes 2 arguments (a and b). Then anything that is a tab or more after the line of the keyword def is in the function.

For example :

def add (a, b):
  c = a + b
  return c
a = 5

The line a = 5 is not in the add function. The latter (the function), calculates the sum of a and b, and stores it in a variable c. Then it returns the value of c with the return.

Function call

Now that we have written functions, we must be able to use them. You can call functions using its identifier, and parentheses.

input ()

In progress, you used the input function to wait for user input, and suddenly pause your program.

In the parentheses, we put the arguments. There are several ways:

  • Or in the order add (5, 2)
  • Either by specifying the variables add (a = 5, b = 2) or add (b = 2, a = 5)

Variables can be written in place of numbers:

a = 5
b = 8
add (a, b) # or add (b, a)

The returned value is stored directly after the function call, so we can nest them:

add (5, add (2, 3)) # 5 + (2 + 3)

We can even recover the result through the classic assignment:

a = 5
result = add (a, 5)

The result variable therefore contains 10.

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