Python控制结构

时间：2011-04-22

来源：qiang.xu

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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');