Python中的迴圈退出舉例及while迴圈舉例
迴圈退出
for迴圈：
for iterating_var in sqquence:
statement(s)
else:
statement(s)
for 迴圈如果正常結束，都會執行else語句。
指令碼1:
#!/usr/bin/env python
for i in xrange(10):
print i
else:
print "main end"
結果：
[root@localhost 20171227]# python exit.py
0
1
2
3
4
5
6
7
8
9
main end
[root@localhost 20171227]#
指令碼2:
#!/usr/bin/env python
import time
for i in xrange(10):
print i
time.sleep(1)
else:
print "main end"
結果：（中途按ctrl+c中斷）
[root@localhost 20171227]# python exit.py
0
1
2
3
4
^CTraceback (most recent call last):
File "exit.py", line 6, in <module>
time.sleep(1)
KeyboardInterrupt
[root@localhost 20171227]#
指令碼3:
沒正常結束：
#!/usr/bin/env python
import time
for i in xrange(10):
print i
if i == 5:
break
else:
print "main end"
結果：
[root@localhost 20171227]# python exit.py
0
1
2
3
4
5
[[email protected] 20171227]#
指令碼4：（跳過本次迴圈continue）
#!/usr/bin/env python
import time
for i in xrange(10):
if i == 3 :
continue
if i == 5:
break
print i
else:
print "main end"
結果：
[[email protected] 20171227]# python exit.py
0
1
2
4
[[email protected] 20171227]#
指令碼5:(pass 什麼都不作)
#!/usr/bin/env python
import time
for i in xrange(10):
if i == 3 :
continue
elif i == 5:
break
elif i ==6:
pass #類似shell 中的：
print i
else:
print "main end"
指令碼6:
#!/usr/bin/env python
import time
import sys
for i in xrange(10):
if i == 3 :
continue
elif i == 5:
continue
elif i ==6:
pass
elif i ==7:
sys.exit()
print i
else:
print "main end"
print "hahaha"
結果：
[[email protected] 20171227]# python exit.py
0
1
2
4
6
[[email protected] 20171227]#
PIP顯示第三方包
[[email protected] 20171227]# pip list
DEPRECATION: The default format will switch to columns in the future. You can use --format=(legacy|columns) (or define a format=(legacy|columns) in your pip.conf under the [list] section) to disable this warning.
backports.ssl-match-hostname (3.4.0.2)
chardet (2.2.1)
configobj (4.7.2)
decorator (3.4.0)
iniparse (0.4)
IPy (0.75)
ipython (1.2.1)
jsonschema (2.5.1)
kitchen (1.1.1)
langtable (0.0.31)
matplotlib (1.2.0)
作業：猜數字遊戲
系統生成一個20以內的隨機整數。
玩家有6次機會進行猜猜看，每次猜測都有反饋（猜大了，猜小了，猜對了-結束）
6次中，猜對了，玩家贏了。
否則系統贏了**。**
In [1]: import random
In [2]: random.ran
random.randint random.random random.randrange
In [2]: random.randint(1,20)
Out[2]: 14
In [3]: random.randint(1,20)
Out[3]: 6
流程控制-while舉例
while與for相對比：
for迴圈用在有次數的迴圈上。
while迴圈用在有條件的控制上。
while迴圈：
while迴圈，直到表示式變為假，才退出。while迴圈，表示式是一個邏輯表示式，必須返回一個True或False
語法：
while expression:
statement(s)
練習指令碼如果下：
指令碼1:
#!/usr/bin/python
n = 0
while 1:
if n == 10:
break
print n, 'hellow'
n +=1
結果：
[[email protected] 20171227]# python while.py
0 hellow
1 hellow
2 hellow
3 hellow
4 hellow
5 hellow
6 hellow
7 hellow
8 hellow
9 hellow
[[email protected] 20171227]#
指令碼2：
#!/usr/bin/python
while 1:
print 'hellow'
input=raw_input("please input sth,q for exit.")
if input == "q":
break
結果：
[[email protected] 20171227]# python while.py
hellow
please input sth,q for exit.s
hellow
please input sth,q for exit.3
hellow
please input sth,q for exit.q
[[email protected] 20171227]#
條件 為假時也會退出：
指令碼3:
#!/usr/bin/python
sth=''
while sth != 'q':
print 'hellow'
sth=raw_input("please input sth,q for exit.")
指令碼4:
回車後退出：
#!/usr/bin/python
sth=''
while sth != 'q':
print 'hellow'
sth=raw_input("please input sth,q for exit.")
if not sth:
break
指令碼5:
#!/usr/bin/python
sth=''
while sth != 'q':
print 'hellow'
sth=raw_input("please input sth,q for exit.")
if not sth:
break
else:
print 'world'
結果：
[[email protected] 20171227]# python while.py
hellow
please input sth,q for exit.q
world
[[email protected] 20171227]#
指令碼6:
#!/usr/bin/python
sth=''
while sth != 'q':
print 'hellow'
sth=raw_input("please input sth,q for exit.")
if not sth:
break
if sth == 'quit':
continue
print 'continue'
else:
print 'world'
結果：
[[email protected] 20171227]# python while.py
hellow
please input sth,q for exit.ss
continue
hellow
please input sth,q for exit.df
continue
hellow
please input sth,q for exit.quit
hellow
please input sth,q for exit.q
continue
world