python学习笔记二：流程控制

2019-11-14 17:26:55

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一、if else：

#!/usr/bin/pythonx = int(raw_input('please input:'))if x >= 90:    if x >= 95:        PRint 'a+'    else:        print 'a'elif x >= 80:    if x >= 85:        print 'b+'    else:        print 'b'elif x >= 70:    if x >= 75:        print 'c+'    else:        print 'c'else:    if x >= 60:        print 'd+'    else:        print 'bad'

二、逻辑运算符 and or not

#!/usr/bin/pythonx = int(raw_input('please input x:'))y = int(raw_input('please input y:'))if x >= 90 and y >= 90:    print 'a'elif x >= 80 or y >= 80:    print 'b'elif not x < 60 and (not y < 60):    print 'c'else:    print 'bad'

三、for

序列：

#!/usr/bin/pythons = "hello python"for x in s:    print xfor index in range(len(s)):    print s[index]

字典：

#!/usr/bin/pythondic = {'a':1,'b':2,'c':3}for x in dic:    print x,dic[x]for k,v in dic.items():    print k,v

控制

else：for正常执行完会执行else中的内容，否则不会（如下面的代码执行过程按Ctrl+c）

#!/usr/bin/pythonimport timefor x in range(10):    print x    time.sleep(1)else:    print 'end'

break：跳出当前这层循环

#!/usr/bin/pythonfor x in range(10):    print x    if x == 6:        breakelse:    print 'end'

这里不会执行else中的内容

pass：占位

exit：退出

#!/usr/bin/pythonfor x in range(10):    print x    if x == 2:        print 'hello',x        continue    if x == 4:        pass    if x == 5:        exit()    if x == 6:        break    print '*'*10else:    print 'end'

四、while

当条件失败，正常结束会执行，执行break后else中不执行

#!/usr/bin/pythonx = 'hello'while x != "q":    print x    x = raw_input('please input something,q for quit:')    if not x:        breakelse:    print 'ending'