控制语句
if/elif/else
if语句和一般编程语言一样，条件为true 执行
如： if true :
print 'true' <----if、else下对齐，要使用相同的空格或者tab
else:
print 'false'
但是，python有自己的特点:
1. if else 要求严格分层对齐 对于嵌套if、else语句都应当严格分层对齐。
2.if else 关键字后边一定要加冒号 ：
#!/usr/bin/python
'''
create By to be crazy
All rights Reserved '''
score=int(raw_input("Enter your score please\n"))
if (score>0 and score<100 ):
if(score>90):
print "your score is A"
elif(score>60):
print "your score is B"
else:
print "your score is C"
else:
print "your score is not correct"
可以看出，if嵌套如何匹配else的，第一层if使用一个tab对齐，第二层使用一个空格对齐，切记elif
循环结构
while/for
for 适用于list和dictionary的遍历，也可以是字符串遍历
word = "Programming is fun!" for letter in word:
# Only print out the letter i
if letter == "i":
print letter
for item in [1, 3, 21]:
print item
webster = {
"Aardvark" : "A star of a popular children's cartoon show.",
"Baa" : "The sound a goat makes.",
"Carpet": "Goes on the floor.",
"Dab": "A small amount."
}
# Add your code below!
for key in webster:
print webster[key]
for 可以配合range()使用
for i in range(10):
print i
print 0~9
for loop 遍历dictionary
d = {'x': 9, 'y': 10, 'z': 20}
for key in d:
if d[key] == 10
print "This dictionary has the value 10!"
while 循环
先检查condition是否为true，为ture就继续循环
loop_condition = True while loop_condition:
print "I am a loop"
loop_condition = False
while/else
while/else 不同于if/else 当循环的条件为False，else语句块会被执行也就是循环从未被执行或在循环正常结束时，都会执行else，如果循环被中断,return、break了，则不执行else。
import random print "Lucky Numbers! 3 numbers will be generated."
print "If one of them is a '5', you lose!" count = 0
while count < 3:
num = random.randint(1, 6)
print num
if num == 5:
print "Sorry, you lose!"
break
count += 1
else:
print "You win!"
当执行到break，就不执行else
若循环正常结束，执行else
需要注意：不要忘记for和while语句的冒号
break/continue
break 跳出循环
count = 0 while True:
print count
count += 1
if count >= 10:
break #exit the current loop.