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');
2.4 Lambda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));
