Python控制结构

1. Python控制结构简介

2. 定义函数

<1>. Python控制结构

1.1 if

print("#############if statement###############");

x = int(input("Enter an integer :"));

if x < 0 :

x = 0;

print("Negative changed to zero .");

elif x == 0 :

print("Zero");

elif x == 1 :

print("Single");

else :

print("None");

1.2 for

############################for statement

print("#############for statement###############");

a = ['cat', 'window', 'defenestrate'];

for x in a :

print(x, len(x));

print("#############range function###############");

for i in range(5) :

print(i);

a = ['Mary', 'had', 'a', 'little', 'lamb'];

for i in range(len(a)) :

print(i, a[i]);

1.3 break and continue

print("#############break and continue###############");

for n in range(2, 10) : # 2 - 9

for x in range(2, n):

if n % x == 0 :

print(n, 'equals', x, '+', n // x);

break;

else :

print(n);

1.4 pass

# ########################pass action test ##############

if False :

pass; ''' do nothing '''

<2>. 定义函数

2.1 定义函数基础

# define the function

def fib(n):

# print the Fibonacci series up to n.

a, b = 0, 1;

while a < n :

print a;

a, b = b, a +b;

2.2 函数默认参数

'''

default arguments

'''

def ask_ok(prompt, retries = 4, complaint = 'Yes or no, please') :

while True:

ok = raw_input(prompt);

if ok in ['y', 'Y', 'yes'] :

return True;

if ok in ['n', 'no', 'nop'] :

return False;

retries = retries - 1;

if retries < 0:

raise IOError('refusenik user');

print complaint;

2.3 不定参数

'''

Arbitrary arguments function

'''

def arbitraryArgsFunc(arg1, *args):

# just print the arbitrary arguments

for i in range(0, len(args)):

print(args[i]);

arbitraryArgsFunc('arg1', 'arg2', 'arg3');

2.4Lambda表达式

'''

lamba function, just like the function template

'''

def make_incrementor(n):

return lambda x:x + n;

f = f = make_incrementor(42);

print(f(0));