blocks|key|1659270|text|如果您只有一个对列表的引用，则以下操作可能会更容易：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1659271|bool_list+=+[False]+*+len(bool_list)|code-block|syntax|javascript|1659272|这将创建一个用False元素填充的新列表。|offset|length|style|CODE|1659273|有关类似的示例，请参阅我对Python+dictionary+clear的回答。|1659274|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/369898/python-dictionary-clear#369925^0|0|0|7|5|0|D|N|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|X|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Y|8|@$I|Z|J|10|K|L]]|9|@]|A|$]]|$1|M|3|N|5|6|7|11|8|@]|9|@$I|12|J|13|1|14]]|A|$]]|$1|O|3|-4|5|6|7|15|8|@]|9|@]|A|$]]]|P|$Q|$5|R|S|T|A|$U|V]]]]

If you only have one reference to the list, the following may be easier:

<pre><code>bool_list = [False] * len(bool_list)
</code></pre>

This creates a new list populated with <code>False</code> elements.

See my answer to <a href="https://stackoverflow.com/questions/369898/python-dictionary-clear#369925">Python dictionary clear</a> for a similar example.

blocks|key|1659313|text|我不会用射程和镜头。使用enumerate()要干净得多|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1659314|for+i,+v+in+enumerate(bool_list):+#i,+v+=+index+and+value
++++bool_list[i]+=+False|code-block|syntax|javascript|1659315|在这种情况下，它留下了一个未使用的变量，但在我看来，它仍然看起来更干净。在性能上也没有明显的变化。|1659316|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

I wouldn't use the range and len. It's a lot cleaner to use enumerate()

<pre><code>for i, v in enumerate(bool_list): #i, v = index and value
 bool_list[i] = False
</code></pre>

It's left with an unused variable in this case, but it still looks cleaner in my opinion. There's no noticeable change in performance either.

blocks|key|1444653|text|对于int、bool和string这样的值类型，你的第二个例子就像它能得到的一样漂亮。您的第一个示例将适用于任何引用类型，如类、字典或其他列表。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1444654|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

For value types such as int, bool and string, your 2nd example is about as pretty as its going to get. Your first example will work on any reference types like classes, dicts, or other lists.

blocks|key|1444727|text|如果您愿意使用numpy数组，使用数组切片实际上很容易做到这一点。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1444728|import+numpy

bool_list+=+numpy.zeros((100,),+dtype=numpy.bool)

#+do+something+interesting+with+bool_list+as+if+it+were+a+normal+list

bool_list[:]+=+False
#+all+elements+have+been+reset+to+False+now|code-block|syntax|javascript|1444729|entityMap|0|LINK|mutability|MUTABLE|url|http://numpy.scipy.org/^0|7|5|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]]|C|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]]]

If you're willing to use <a href="http://numpy.scipy.org/" rel="nofollow noreferrer">numpy</a> arrays, it's actually really easy to do things like this using array slices.

<pre><code>import numpy

bool_list = numpy.zeros((100,), dtype=numpy.bool)

# do something interesting with bool_list as if it were a normal list

bool_list[:] = False
# all elements have been reset to False now
</code></pre>

blocks|key|1444753|text|这是另一个版本：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1444754|bool_list+=+[False+for+item+in+bool_list]|code-block|syntax|javascript|1444755|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Here's another version:

<pre><code>bool_list = [False for item in bool_list]
</code></pre>

blocks|key|1444813|text|我认为|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1444814|bool_list+=+[False+for+element+in+bool_list]|code-block|syntax|javascript|1444815|就像它能做到的那样。在python中使用这样的列表通常也会比使用for循环更快。|1444816|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

I think 

<pre><code>bool_list = [False for element in bool_list]
</code></pre>

is as pythonic as it gets. Using lists like this should generaly be faster then a for loop in python too.

blocks|key|1444822|text|bool_list[:]+=+[False]+*+len(bool_list)|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1444823|或|unstyled|1444824|bool_list[:]+=+[False+for+item+in+bool_list]|1444825|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|L|8|@]|9|@]|A|$]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$B|C]]|$1|I|3|-4|5|F|7|N|8|@]|9|@]|A|$]]]|J|$]]

<pre><code>bool_list[:] = [False] * len(bool_list)
</code></pre>

or

<pre><code>bool_list[:] = [False for item in bool_list]
</code></pre>

I have a list of booleans where occasionally I reset them all to false. After first writing the reset as:

<pre><code>for b in bool_list:
 b = False
</code></pre>

I found it doesn't work. I spent a moment scratching my head, then remembered that of course it won't work since I'm only changing a reference to the bool, not its value. So I rewrote as:

<pre><code>for i in xrange(len(bool_list)):
 bool_list[i] = False
</code></pre>

and everything works fine. But I found myself asking, "Is that really the most pythonic way to alter all elements of a list?" Are there other ways that manage to be either more efficient or clearer?

Alter elements of a list

我有一个布尔值列表，有时我会将它们全部重置为false。在第一次将重置写为：for b in bool_list:    b = False我发现它不起作用。我花了片刻的时间挠头，然后记起它当然不会起作用，因为我只改变了对bool的引用，而不是它的值。所以我重写为：for i in xrange(len(bool_li...

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