列表理解中的'while'？ [英] 'while' in list comprehension?
问题描述
你好，
除了
''之外还有一个''while''条件是否有用'''''在列表推导中？
foo = []
for i in bar：
if len（i）== 0：
休息
foo.append（i）
然后变成
foo = [i for i in bar而len（i）> 0]
有没有理由没有这种东西？我实际上很多时候会错过它。
干杯，jsaul
jsaul问...然后会变成
foo = [i for i in bar而len（i）> 0]
有没有理由没有这种东西？我实际上经常想念它。
这有什么不同：
foo = [i for i in bar in if len（i）]
Emile van Sebille
em *** @ fenx.com
foo = [i for i in bar而len（i）> 0 ]
Emile>这有什么不同：
Emile> foo = [i for i in bar if len（i）]
第一个是：
_ = []
for i in bar：
if if（len（i）> 0）：
break
_.append （i）
返回_
第二个是：
_ = []
for i in bar：
if len（i）> 0：
_.append（i）
返回_
跳过
使用2.3'的itertools：
foo = [i for ite in itertools.takewhile（lambda i：len（i）> 0，bar）]
或者
foo = list（itertools.takewhile（len，bar）]
甚至
foo = itertools .takewhile（len，bar）#a iterable，not a list
Jeff
Hi there,
wouldn''t it be useful to have a ''while'' conditional in addition to
''if'' in list comprehensions?
foo = []
for i in bar:
if len(i) == 0:
break
foo.append(i)
would then turn into
foo = [ i for i in bar while len(i)>0 ]
Is there any reason for not having this kind of thing? I actually
miss it pretty often.
Cheers, jsaul
jsaul asks...would then turn into
foo = [ i for i in bar while len(i)>0 ]
Is there any reason for not having this kind of thing? I actually
miss it pretty often.
How is this different from:
foo = [ i for i in bar if len(i) ]
Emile van Sebille
em***@fenx.com
foo = [ i for i in bar while len(i)>0 ]
Emile> How is this different from:
Emile> foo = [ i for i in bar if len(i) ]
The first is like:
_ = []
for i in bar:
if not (len(i) > 0):
break
_.append(i)
return _
The second is like:
_ = []
for i in bar:
if len(i) > 0:
_.append(i)
return _
Skip
Use 2.3''s itertools:
foo = [i for i in itertools.takewhile(lambda i: len(i) > 0, bar)]
or maybe
foo = list(itertools.takewhile(len, bar)]
or even
foo = itertools.takewhile(len, bar) # an iterable, not a list
Jeff
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