Python流程控制代码详解

x=int(input('请输入一个数字：'))
while x>0:
 print('正数')
 break

x=int(input('请输入一个数字：'))
if x<0:
 print('负数')
elif x==0:
 print('零')
else :
 print('正数')

x=['a','b','c','d']for i in x : 
 # i 位置的字符，只要不是关键字，可以随意用字符代表
 print(i)

class range(object):
 """
 range(stop) -> range object
 range(start, stop[, step]) -> range object
 
 Return an object that produces a sequence of integers from start (inclusive)
 to stop (exclusive) by step. range(i, j) produces i, i+1, i+2, ..., j-1.
 start defaults to 0, and stop is omitted! range(4) produces 0, 1, 2, 3.
 These are exactly the valid indices for a list of 4 elements.
 When step is given, it specifies the increment (or decrement).
 """
 def count(self, value): # real signature unknown; restored from doc
 """ rangeobject.count(value) -> integer -- return number of occurrences of value """
 return 0

 def index(self, value, start=None, stop=None): # real signature unknown; restored from doc
 """
 rangeobject.index(value, [start, [stop]]) -> integer -- return index of value.
 Raise ValueError if the value is not present.
 """
 return 0

 def contains(self, *args, **kwargs): # real signature unknown
 """ Return key in self. """
 pass

 def eq(self, *args, **kwargs): # real signature unknown
 """ Return self==value. """
 pass

 def getattribute(self, *args, **kwargs): # real signature unknown
 """ Return getattr(self, name). """
 pass

 def getitem(self, *args, **kwargs): # real signature unknown
 """ Return self[key]. """
 pass

 def ge(self, *args, **kwargs): # real signature unknown
 """ Return self>=value. """
 pass

 def gt(self, *args, **kwargs): # real signature unknown
 """ Return self>value. """
 pass

 def hash(self, *args, **kwargs): # real signature unknown
 """ Return hash(self). """
 pass

 def init(self, stop): # real signature unknown; restored from doc
 pass

 def iter(self, *args, **kwargs): # real signature unknown
 """ Implement iter(self). """
 pass

 def len(self, *args, **kwargs): # real signature unknown
 """ Return len(self). """
 pass

 def le(self, *args, **kwargs): # real signature unknown
 """ Return self<=value. """
 pass

 def lt(self, *args, **kwargs): # real signature unknown
 """ Return self<value. """
 pass

 @staticmethod # known case of new
 def new(*args, **kwargs): # real signature unknown
 """ Create and return a new object. See help(type) for accurate signature. """
 pass

 def ne(self, *args, **kwargs): # real signature unknown
 """ Return self!=value. """
 pass

 def reduce(self, *args, **kwargs): # real signature unknown
 pass

 def repr(self, *args, **kwargs): # real signature unknown
 """ Return repr(self). """
 pass

 def reversed(self, *args, **kwargs): # real signature unknown
 """ Return a reverse iterator. """
 pass

 start = property(lambda self: object(), lambda self, v: None, lambda self: None) # default

 step = property(lambda self: object(), lambda self, v: None, lambda self: None) # default

 stop = property(lambda self: object(), lambda self, v: None, lambda self: None) # default

for i in range(3): #运行

while True:
 print('hello')
 break

for x in range(1, 4):
 print(x, 'for语句')
 continue
 print(x, 'continue语句后')
else:
 print(x, 'else语句')
 
#运行结果
for语句
for语句
for语句
else语句

for x in range(1, 4):
 print(x)
else:
 print(x)

#运行结果
2
3

class EmptyClass：
 pass