Introduces functions prams and arguments. How to define and use founctions.

Week 4 Functions

1.Stored (and reused) Steps

def hello(): #定义函数(store)
    print 'Hello'
    print 'Fun'
    
hello() #调用函数(reuse)
print 'Zip'
hello() #调用函数(reuse)

Type Conversion
Built in functions int() and float()

2.Python Functions

2.1. Built in functions that are provided

-input: raw_input()
-type conversions: type()
-string conversions: str() int()

2.2. Defined functions

-arguments as input
-def to define

big= max('Hello world') #定义函数 不会执行
print big #调用函数 执行

Names of built in function == New reserved words

3.Arguments

• is a value pass into the function
• need to be in the ()

3.1 Parameters

A parameter is a variable which we use in the functions

definition that is a “handle” that allows the code in the function to access the arguments for a particular function invocation.

        def greet(lang):
            if lang == 'es':
               print 'Hola’
            elif lang == 'fr':
               print 'Bonjour’
            else:
               print 'Hello’
    greet('en')Hello
    greet('es')Hola
    greet('fr')Bonjour

3.2 Return Values

Often a function will take its arguments, do some computation and return a value to be used as the value of the function call in the calling expression. The return keyword is used for this.

>>> def greet(lang):
...         if lang == 'es':
...            return 'Hola’
...         elif lang == 'fr':
...            return 'Bonjour’
...         else:
...            return 'Hello’
... >>> print greet('en'),'Glenn’
Hello Glenn
>>> print greet('es'),'Sally’
Hola Sally
>>> print greet('fr'),'Michael’
Bonjour Michael
>>>