我需要在Python程序中模拟do-while循环.不幸的是,以下简单的代码不起作用:
list_of_ints = [ 1, 2, 3 ]
iterator = list_of_ints.__iter__()
element = None
while True:
if element:
print element
try:
element = iterator.next()
except StopIteration:
break
print "done"
而不是"1,2,3,完成",它打印以下输出:
[stdout:]1
[stdout:]2
[stdout:]3
None['Traceback (most recent call last):
', ' File "test_python.py", line 8, in <module>
s = i.next()
', 'StopIteration
']
我能做些什么来捕获'stop iteration'异常并正确地打破while循环？
以下将伪代码示为可能需要这样的事物的示例.
状态机:
s = ""
while True :
if state is STATE_CODE :
if "//" in s :
tokens.add( TOKEN_COMMENT, s.split( "//" )[1] )
state = …这个关于perl中无限循环的问题很感兴趣:while(1)vs.for(;;)有速度差吗？,我决定在python中运行类似的比较.我期望编译器会为while(True): pass和生成相同的字节代码while(1): pass,但实际上并非python2.7中的情况.
以下脚本:
import dis
def while_one():
while 1:
pass
def while_true():
while True:
pass
print("while 1")
print("----------------------------")
dis.dis(while_one)
print("while True")
print("----------------------------")
dis.dis(while_true)
产生以下结果:
while 1
----------------------------
4 0 SETUP_LOOP 3 (to 6)
5 >> 3 JUMP_ABSOLUTE 3
>> 6 LOAD_CONST 0 (None)
9 RETURN_VALUE
while True
----------------------------
8 0 SETUP_LOOP 12 (to 15)
>> 3 LOAD_GLOBAL 0 (True)
6 JUMP_IF_FALSE 4 (to 13)
9 POP_TOP
9 10 JUMP_ABSOLUTE 3
>> 13 POP_TOP …我正在编写一个程序,我要求用户输入.
我希望python检查输入是否为数字(不是单词或puntuation ...),如果它是一个数字,表示我的元组中的对象.如果3个条件中的一个导致False,那么我希望用户为该变量提供另一个值.这是我的代码
colour={'yello':1, 'blue':2, 'red':3, 'black': 4, 'white': 5, 'green': 6}
height_measurements=('centimeter:1', 'inch:2', 'meter:3', 'foot:4')
weight_measurements=('gram:1', 'kilogram:2', 'pounds:3')
print height_measurements
hm_choice = raw_input('choose your height measurement').lower()
while not hm_choice.isdigit() or hm_choice > 0 or hm_choice < len(height_measurements) :
hm_choice = raw_input('choose your height measurement').lower()
print weight_measurements
wm_choice = raw_input('choose your weight measurement').lower()
while not wm_choice.isdigit() or wm_choice > 0 or wm_choce < len(weight_measurements) :
wm_choice = raw_input('choose your weight measurement').lower()
当我把它测试时,无论我放入什么,它都会让我不断地为height_measurement插入输入
请检查我的代码并为我更正.如果你愿意,请为我提供更好的代码.