Python流程控制与函数

if

>>> x = int(raw_input("Please enter an integer：")) 
Please enter an integer：42
>>> if x < 0:
...     x = 0
...     print "变为0"
... elif x == 0:
...     print "0"
... elif x == 1:
...     print "Single"
... else:
...     print "More"
... 
More

for

# Measure some strings:
a = ['cat', 'window', 'defenestrate']
for x in a:
    print x, len(x)

range() 函数

>>> range(10)
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> range(5,10)
[5, 6, 7, 8, 9]
>>> range(0,10,3)
[0, 3, 6, 9]

a = ['PHP', 'Java', 'Python']
for i in range(len(a)):
    print i, a[i]

break continue

break用于跳出最近的一个for

定义函数

>>> def fib(n):
...     a,b = 0,1
...     while a<n:
...             print a,
...             a,b = b,a+b
... 
>>> fib(100)
0 1 1 2 3 5 8 13 21 34 55 89
>>> f = fib
>>> f(100)
0 1 1 2 3 5 8 13 21 34 55 89

带参数的函数

def ask_ok(prompt, retries=4, complaint='Yes or no,please!'):
    while True:
        ok = raw_input(prompt)
        if ok in ('y', 'ye', 'yes'):
            return True
        if ok in ('n', 'no'):
            return False
        retries = retries - 1
        if retries < 0:
            raise IOError('refuse user')
        print complaint


ask_ok('yes', 5, 'Yes or no!')