问题描述
我想念能用Python做这样的事情
1f（I = a.find（" 3"）））！= -1：
打印它在这里：，我
其他：
打印No 3'在这里
我在其中分配了find（）返回的索引，并且if语句获得了
来在同一行中完成它的工作。然后你不必拥有另一个像
那样专门得到3的索引。有没有办法在
Python中做到这一点？
谢谢！
Bob
I miss being able to do something like this in Python
1f (I = a.find("3")) != -1:
print "It''s here: ", I
else:
print "No 3''s here"
where I gets assigned the index returned by find() AND the if statement gets
to do its job in the same line. Then you don''t have to have another like
that specifically gets the index of the "3". Is there a way to do this in
Python?
Thanks!
Bob
推荐答案
这是Python中一个深思熟虑的基本设计决定
赋值是一种陈述，而不是具有副作用的表达。这个
意味着你经常需要一个额外的与经典的C"分配
和测试相比较如上所述的成语。我和你一样，经常会错过这个C成语的紧凑性，但它确实存在。
将魔法值恢复到魔法值也是unpythonic表示失败。
抛出异常将是更正常的做法。所以，
我希望以上内容可以转化为：
尝试：
i = a.find（ 3）
打印它在这里：，我是
打印No 3 '在这里'
It is a deliberate and fundamental design decision in Python that
assignment is a statement, not an expression with side effects. This
means you often need an "extra" line compared to a classic C "assign
and test" idiom such as you have above. I, like you, often miss the
compactness of the C idiom, but there it is.
It''s also unpythonic to return magic values to indicate failure.
Throwing an exception would be the more normal way of doing it. So,
I''d expect the above to translate into something like:
try:
i = a.find("3")
print "It''s here: ", i
except NotFound:
print "No 3''s here"
这是Python中一个深思熟虑的基本设计决策，
赋值是一个语句，而不是一个表达式副作用。这意味着你经常需要一个额外的东西。线条与经典C分配
和测试相比较如上所述的成语。我和你一样，经常会错过C语言的紧凑性，但它确实存在。
返回神奇的值以表示失败也是单声道的。
投掷一个例外是更正常的做法。所以，
我希望以上内容能够转化为：
尝试：
i = a.find（" 3"）
print" ;它在这里：，我是
除了NotFound：
打印No 3'在这里
It is a deliberate and fundamental design decision in Python that
assignment is a statement, not an expression with side effects. This
means you often need an "extra" line compared to a classic C "assign
and test" idiom such as you have above. I, like you, often miss the
compactness of the C idiom, but there it is.
It''s also unpythonic to return magic values to indicate failure.
Throwing an exception would be the more normal way of doing it. So,
I''d expect the above to translate into something like:
try:
i = a.find("3")
print "It''s here: ", i
except NotFound:
print "No 3''s here"
坚果。我想你是对的。这不合适。每天为Python添加的东西或者每天都会提出我不能发音的东西，但是一个简单的''如果
（I = a.find（" 3" 3） ;））！= -1''是不允许的。呵呵。可能是时候回到
到BASIC了。 :)
如果.find（）被.index（）替换，我认为你的方式会奏效。我是
只是想稍微清理一下if / elif树，所以使用try会使
更大的东西。
谢谢！
Bob
Nuts. I guess you''re right. It wouldn''t be proper. Things are added or
proposed every day for Python that I can''t even pronounce, but a simple ''if
(I = a.find("3")) != -1'' isn''t allowed. Huh. It might be time to go back
to BASIC. :)
I think your way would work if .find() were replaced with .index(). I''m
just trying to clean up an if/elif tree a bit, so using try would make
things bigger.
Thanks!
Bob
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