A function is a block where you input values and then you get an output (result). The structure of a function is the following:
def FunctionName(arg1, arg2 , ...): [Body] ... return Output
You need to use a valid function name (FunctionName), it's not allowed to call it with number, or with a predefined name. The arguments (arg1, arg2, …) are the inputs of your function, you need to put them a valid name as well. Inside the body you develop your calculations or algorithm. Finally you need to return your output, you do it using a reserved word return.
In python the indentation is a big deal, putting this way, if you are a programmer, it's like a comma in C. So don't forget to use it as well as the colon.
Before to start. I create a file called: myfirtsfunction.py in whichever editor that you prefer (some alternatives here).
Here goes the example.
def sumar(a,b): # input arguments a, b c = a + b # the sum is assigned to c return c # c is returned
It returns the sum between two numbers:
>>> sumar(3,54) 57
Here goes another example. Let's round a number without using the predefined python function (round).
def roundnum(num): num = num + 0.5 # Round the integer part num = str(num) # Convert real to string index = num.find('.') # Get the index of the period num = num[:index] # Get the integer part as a string yet return int(num) # Convert string to integer
Output:
>>> print roundnum(5.6) 6 >>> print roundnum(5.3) 5