Python学习笔记2（函数）

#callback 判断是否存在
import match
x = 1
y = math.sqrt

callable(x)
#False
callable(y)
#True

#函数
def fib(num):
    result = [0,1]
    for i in range(num-2):
        result.append(result[-2],result[-1])
        return result;

fibs(10)
#[0,1,1,2,3,5,8,13,21,34]

#函数文档
def square(x):
    'Calcutates the square of the number x'
    return x*x

square.__doc__
#'Calcutates the square of the number x'

#None
 def test():
     print 'This is printed'
     return
     print 'This is not'

x = test()
#This is printed

print x 
#None

#改变列表
def change(n):
    n[0] = 'Mr.Gumby'

names = ['Mr.Entiy','Mrs.Thing']
change(names)
print names
#['Mr,Gumby','Mrs.Thing']

#复制列表
names = ['1','2']
n = names[:]

n is names
#False
n == names
#True

#位置参数
def hello_1(greeting,name):
    print '%s,%s!' % (greeting,name)

def hello_2(name,greeting):
    print '%s,%s!' % (name,greeting)

hello_1('Hello','World')
#Hello,World
hello_2('Hello','World')
#Hello,World
hello_2(greeting='Hello',name='World')
#World,Hello

#收集参数

def print_params(title,*params):
    print title
    print params

print_params('params:',1,2,3)
#params:
#(1,2,3)

def print_params2(title,**params):
    print title
    print params

print_params2('params:',x=1,y=2,z=3)
#{'z':3,'x':1,'y':2}