blocks|key|339233|text|如果您实际上希望函数的行为类似于str()内置函数，但在参数为None时返回空字符串，请执行以下操作：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|339234|def+xstr(s):
++++if+s+is+None:
++++++++return+''
++++return+str(s)|code-block|syntax|javascript|339235|entityMap^0|G|5|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

If you actually want your function to behave like the <code>str()</code> built-in, but return an empty string when the argument is None, do this:

<pre><code>def xstr(s):
 if s is None:
 return ''
 return str(s)
</code></pre>

blocks|key|341835|text|可能最短的应该是str(s+or+'')|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|341836|因为没有一个是假的，如果x是假的，"x或y“返回y。有关详细说明，请参阅Boolean+Operators。它很简短，但不是很明确。|341837|entityMap|0|LINK|mutability|MUTABLE|url|http://docs.python.org/library/stdtypes.html#boolean-operations-and-or-not^0|8|C|0|10|H|0|0^^$0|@$1|2|3|4|5|6|7|P|8|@$9|Q|A|R|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|S|8|@]|D|@$9|T|A|U|1|V]]|E|$]]|$1|H|3|-4|5|6|7|W|8|@]|D|@]|E|$]]]|I|$J|$5|K|L|M|E|$N|O]]]]

Probably the shortest would be 
<code>str(s or '')</code>

Because None is False, and "x or y" returns y if x is false. See <a href="http://docs.python.org/library/stdtypes.html#boolean-operations-and-or-not" rel="noreferrer">Boolean Operators</a> for a detailed explanation. It's short, but not very explicit.

blocks|key|341706|text|def+xstr(s):
++++return+''+if+s+is+None+else+str(s)|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|341707|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>def xstr(s):
 return '' if s is None else str(s)
</code></pre>

blocks|key|339310|text|如果您知道该值将始终为字符串或无：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|339311|xstr+=+lambda+s:+s+or+""

print+xstr("a")+%2B+xstr("b")+#+->+'ab'
print+xstr("a")+%2B+xstr(None)+#+->+'a'
print+xstr(None)+%2B+xstr("b")+#+->+'b'
print+xstr(None)+%2B+xstr(None)+#+->+''|code-block|syntax|javascript|339312|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|$]]

If you know that the value will always either be a string or None:

<pre><code>xstr = lambda s: s or ""

print xstr("a") + xstr("b") # -&gt; 'ab'
print xstr("a") + xstr(None) # -&gt; 'a'
print xstr(None) + xstr("b") # -&gt; 'b'
print xstr(None) + xstr(None) # -&gt; ''
</code></pre>

blocks|key|338381|text|return+s+or+''可以很好地解决你所说的问题！|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|338382|entityMap^0|0|E|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|K|8|@]|D|@]|E|$]]]|G|$]]

<code>return s or ''</code> will work just fine for your stated problem!

blocks|key|336959|text|def+xstr(s):
+++return+s+or+""|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|336960|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>def xstr(s):
 return s or ""
</code></pre>

blocks|key|338291|text|函数式方法(一行)|type|unstyled|depth|inlineStyleRanges|entityRanges|data|338292|xstr+=+lambda+s:+''+if+s+is+None+else+s|code-block|syntax|javascript|338293|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|$]]

Functional way (one-liner)

<pre><code>xstr = lambda s: '' if s is None else s
</code></pre>

blocks|key|3106657|text|在其他一些答案的基础上，提供一个简洁的一行代码来实现这一点：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3106658|s+=+(lambda+v:+v+or+'')(a)+%2B+(lambda+v:+v+or+'')(b)|code-block|syntax|javascript|3106659|或者仅仅是：|3106660|s+=+(a+or+'')+%2B+(b+or+'')|3106661|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

A neat one-liner to do this building on some of the other answers:

<pre><code>s = (lambda v: v or '')(a) + (lambda v: v or '')(b)
</code></pre>

or even just:

<pre><code>s = (a or '') + (b or '')
</code></pre>

blocks|key|3319426|text|更新：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3319427|我现在主要使用这种方法：|3319428|some_string+=+None
some_string+or+''|code-block|syntax|javascript|3319429|如果some_string不是NoneType，or将在那里短路并返回它，否则它返回空字符串。|offset|length|style|CODE|3319430|旧的：|3319431|Max函数在python+2.x中有效，但在3.x中不起作用：|3319432|max(None,+'')++#+Returns+blank
max("Hello",+'')+#+Returns+Hello|3319433|entityMap^0|0|0|0|F|8|O|2|0|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|X|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|Y|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|Z|8|@$K|10|L|11|M|N]|$K|12|L|13|M|N]]|9|@]|A|$]]|$1|O|3|P|5|6|7|14|8|@]|9|@]|A|$]]|$1|Q|3|R|5|6|7|15|8|@]|9|@]|A|$]]|$1|S|3|T|5|F|7|16|8|@]|9|@]|A|$G|H]]|$1|U|3|-4|5|6|7|17|8|@]|9|@]|A|$]]]|V|$]]

UPDATE:
I mainly use this method now:
<pre><code>some_string = None
some_string or ''
</code></pre>
If some_string was not <code>NoneType</code>, the <code>or</code> would short circuit there and return it, otherwise it returns the empty string.
OLD:
Max function worked in python 2.x but not in 3.x:
<pre><code>max(None, '') # Returns blank
max(&quot;Hello&quot;, '') # Returns Hello
</code></pre>

blocks|key|3319127|text|def+xstr(s):
++++return+{None:''}.get(s,+s)|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|3319128|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>def xstr(s):
 return {None:''}.get(s, s)
</code></pre>

blocks|key|3106544|text|如果您需要与Python+2.4兼容，请对上面的版本进行更改|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3106545|xstr+=+lambda+s:+s+is+not+None+and+s+or+''|code-block|syntax|javascript|3106546|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|$]]

Variation on the above if you need to be compatible with Python 2.4

<pre><code>xstr = lambda s: s is not None and s or ''
</code></pre>

blocks|key|3319500|text|如果是关于格式化字符串，您可以执行以下操作：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3319501|from+string+import+Formatter

class+NoneAsEmptyFormatter(Formatter):
++++def+get_value(self,+key,+args,+kwargs):
++++++++v+=+super().get_value(key,+args,+kwargs)
++++++++return+''+if+v+is+None+else+v

fmt+=+NoneAsEmptyFormatter()
s+=+fmt.format('{}{}',+a,+b)|code-block|syntax|javascript|3319502|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|$]]

If it is about formatting strings, you can do the following:

<pre><code>from string import Formatter

class NoneAsEmptyFormatter(Formatter):
 def get_value(self, key, args, kwargs):
 v = super().get_value(key, args, kwargs)
 return '' if v is None else v

fmt = NoneAsEmptyFormatter()
s = fmt.format('{}{}', a, b)
</code></pre>

blocks|key|338271|text|def+xstr(s):
++++return+s+if+s+else+''

s+=+"%25s%25s"+%25+(xstr(a),+xstr(b))|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|338272|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>def xstr(s):
 return s if s else ''

s = "%s%s" % (xstr(a), xstr(b))
</code></pre>

blocks|key|337008|text|在下面解释的场景中，我们总是可以避免类型转换。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|337009|customer+=+"John"
name+=+str(customer)
if+name+is+None
+++print+"Name+is+blank"
else:+
+++print+"Customer+name+:+"+%2B+name|code-block|syntax|javascript|337010|在上面的例子中，如果变量customer的值为None，那么它在被赋值给'name‘时会进一步进行强制转换。“if”子句中的比较总是失败。|337011|customer+=+"John"+#+even+though+its+None+still+it+will+work+properly.
name+=+customer
if+name+is+None
+++print+"Name+is+blank"
else:+
+++print+"Customer+name+:+"+%2B+str(name)|337012|上面的例子可以正常工作。当从URL、JSON或XML获取值，或者甚至值需要进一步的类型转换以进行任何操作时，这种情况非常常见。|337013|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|S|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

We can always avoid type casting in scenarios explained below.

<pre><code>customer = "John"
name = str(customer)
if name is None
 print "Name is blank"
else: 
 print "Customer name : " + name
</code></pre>

In the example above in case variable customer's value is None the it further gets casting while getting assigned to 'name'. The comparison in 'if' clause will always fail. 

<pre><code>customer = "John" # even though its None still it will work properly.
name = customer
if name is None
 print "Name is blank"
else: 
 print "Customer name : " + str(name)
</code></pre>

Above example will work properly. Such scenarios are very common when values are being fetched from URL, JSON or XML or even values need further type casting for any manipulation.

blocks|key|3106467|text|使用短路评估：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3106468|s+=+a+or+''+%2B+b+or+''|code-block|syntax|javascript|3106469|由于%2B不是一个很好的字符串操作，所以最好使用格式化字符串：|3106470|s+=+"%25s%25s"+%25+(a+or+'',+b+or+'')|3106471|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

Use short circuit evaluation:

<pre><code>s = a or '' + b or ''
</code></pre>

Since + is not a very good operation on strings, better use format strings:

<pre><code>s = "%s%s" % (a or '', b or '')
</code></pre>

blocks|key|338473|text|如果您使用的是python+v3.7，请使用F字符串|type|unstyled|depth|inlineStyleRanges|entityRanges|data|338474|xstr+=+F"{s}"|code-block|syntax|javascript|338475|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|$]]

Use F string if you are using python v3.7

<pre><code>xstr = F"{s}"
</code></pre>

What is the most idiomatic way to do the following?

<pre><code>def xstr(s):
 if s is None:
 return ''
 else:
 return s

s = xstr(a) + xstr(b)
</code></pre>

update: I'm incorporating Tryptich's suggestion to use str(s), which makes this routine work for other types besides strings. I'm awfully impressed by Vinay Sajip's lambda suggestion, but I want to keep my code relatively simple.

<pre><code>def xstr(s):
 if s is None:
 return ''
 else:
 return str(s)
</code></pre>

Python: most idiomatic way to convert None to empty string?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

文章

问答

视频

学习中心

腾讯云实验室

直播

竞赛

腾讯云架构师技术同盟交流圈

腾讯云数据库专区

腾讯云顾问专区

腾讯云原生专区

腾讯混元专区

腾讯云TCE专区

腾讯云Lighthouse专区

腾讯云HAI专区

腾讯云Edgeone专区

腾讯云存储专区

腾讯云智能专区

腾讯轻联专区 

腾讯云开发专区

TAPD专区

腾讯轻量云游戏服专区

腾讯云最具价值专家

腾讯云架构师技术同盟

腾讯云创作之星

腾讯云开发者先锋 

腾讯云代码助手

CODING DevOps

Cloud Studio

SDK中心

API中心

命令行工具

做以下事情最常用的方式是什么？def xstr(s):    if s is None:        return ''    else:        return ss = xstr(a) + xstr(b)更新：我正在整合Tryptich的建议，使用str(s)，这使得这个例程适用于除字符串之外的其他类型。Vinay Sajip的lambda建议给我留下了深刻的印象，但我想让我的代码相对简

问Python:将None转换为空字符串的最常用方法？
EN

回答 16

Stack Overflow用户

Stack Overflow用户

Stack Overflow用户

社区

活动

圈层

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问Python:将None转换为空字符串的最常用方法？EN

回答 16

Stack Overflow用户

Stack Overflow用户

Stack Overflow用户

社区

活动

圈层

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问Python:将None转换为空字符串的最常用方法？
EN