blocks|key|2682981|text|我同意其他答案，但我想在这里解释重要的一点。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2682982|无对象是单例对象。多少次你将无对象赋值给一个变量，同样的对象被使用。所以|offset|length|style|BOLD|2682983|x+=+None
y+=+None|code-block|syntax|javascript|2682984|等于|2682985|x+=+y+=+None|2682986|但是您不应该对python中的任何其他对象执行相同的操作。例如,|2682987|x+=+{}++#+each+time+a+dict+object+is+created
y+=+{}|2682988|不等于|2682989|x+=+y+=+{}++#+same+dict+object+assigned+to+x+,y.+We+should+not+do+this.|2682990|entityMap^0|0|0|1|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|11|8|@$D|12|E|13|F|G]]|9|@]|A|$]]|$1|H|3|I|5|J|7|14|8|@]|9|@]|A|$K|L]]|$1|M|3|N|5|6|7|15|8|@]|9|@]|A|$]]|$1|O|3|P|5|J|7|16|8|@]|9|@]|A|$K|L]]|$1|Q|3|R|5|6|7|17|8|@]|9|@]|A|$]]|$1|S|3|T|5|J|7|18|8|@]|9|@]|A|$K|L]]|$1|U|3|V|5|6|7|19|8|@]|9|@]|A|$]]|$1|W|3|X|5|J|7|1A|8|@]|9|@]|A|$K|L]]|$1|Y|3|-4|5|6|7|1B|8|@]|9|@]|A|$]]]|Z|$]]

I agree with the other answers but would like to explain the important point here.

None object is singleton object. How many times you assign None object to a variable, same object is used. So 

<pre><code>x = None
y = None
</code></pre>

is equal to 

<pre><code>x = y = None
</code></pre>

but you should not do the same thing with any other object in python. For example,

<pre><code>x = {} # each time a dict object is created
y = {}
</code></pre>

is not equal to

<pre><code>x = y = {} # same dict object assigned to x ,y. We should not do this.
</code></pre>

blocks|key|127082|text|首先，我建议你不要这么做。它是不可读的，也不是Pythonic式的。但是，您可以使用以下命令来减少行数：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|127083|details,+product_base,+product_identity,+category_string,+store_id,+image_hash,+image_link_mask,+results+=+[None]+*+8
abort+=+False
data+=+{}|code-block|syntax|javascript|127084|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|$]]

First of all I would advice you not to do this. It's unreadable and un-Pythonic. However you can reduce the number of lines with something like:

<pre><code>details, product_base, product_identity, category_string, store_id, image_hash, image_link_mask, results = [None] * 8
abort = False
data = {}
</code></pre>

blocks|key|2894824|text|(
++++details,
++++producy_base,
++++product_identity,
++++category_string,
++++store_id,
++++image_hash,
++++image_link_mask,
++++results,
)+=+(None,+None,+None,+None,+None,+None,+None,+None)

abort+=+False
data+=+{}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|2894825|我就是这么做的。|unstyled|2894826|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|J|8|@]|9|@]|A|$]]|$1|G|3|-4|5|F|7|K|8|@]|9|@]|A|$]]]|H|$]]

<pre><code>(
 details,
 producy_base,
 product_identity,
 category_string,
 store_id,
 image_hash,
 image_link_mask,
 results,
) = (None, None, None, None, None, None, None, None)

abort = False
data = {}
</code></pre>
That's how I do.

blocks|key|2894904|text|我使用了一个单行的lambda函数来帮助我解决这个问题。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2894905|nones+=+lambda+n:+[None+for+_+in+range(n)]
v,+w,+x,+y,+z+=+nones(5)|code-block|syntax|javascript|2894906|lambda和这个是一样的。|2894907|def+nones(n):
++++return+[None+for+_+in+range(n)]|2894908|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|$]]

I have a one-line lambda function I use that helps me out with this.

<pre><code>nones = lambda n: [None for _ in range(n)]
v, w, x, y, z = nones(5)
</code></pre>

The lambda is the same thing as this.

<pre><code>def nones(n):
 return [None for _ in range(n)]
</code></pre>

blocks|key|2683120|text|混合了之前的答案：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2683121|from+copy+import+deepcopy

def+default(number,+value+=+None):
++++if+type(value)+is+dict+or+object:
++++++++return+[deepcopy(value)+for+_+in+range(number)]
++++else:
++++++++return+[value]+*+number
++++
o,+p,+q,+r,+s+=+default(5)
t,+u+=+default(2,+false)
v,+w,+x+=+default(3,+{})

class+GPU:
++def+__init__(self,+m,+p):
++++self.model+=+m
++++self.price+=+p
+
rtx_3080+=+GPU("RTX+3080",+99999)

y,+z+=+default(2,+rtx_3080)|code-block|syntax|javascript|2683122|编辑|offset|length|style|BOLD|2683123|尝试通过更好地处理具有pandas/numpy类型的可变变量来优化深度复制调用。可能漏掉了一些其他的。如果有人找到了更好的方法来检查易变性，请随意分享。尽管如此，无论你的用例是什么，这都可能是过度设计……|2683124|import+builtins
from+copy+import+deepcopy
from+numbers+import+Number
from+pandas+import+api,+DataFrame

mutables+=+(dict,+list,+set,+DataFrame)
immutables+=+(str,+tuple,+frozenset,+Number)

def+is_built_in_type(var):
++++return+type(var).__name__+in+dir(builtins)

def+is_mutable(var):
++++return+var+is+not+None+and+(api.types.is_list_like(var)+or+isinstance(var,+mutables)+or+not+is_built_in_type(var))

def+is_immutable(var):
++++return+var+is+None+or+isinstance(var,+immutables)

def+default(number,+value=None):
++++if+is_mutable(value):
++++++++return+[deepcopy(value)+for+_+in+range(number)]
++++elif+is_immutable(value):
++++++++return+[value]+*+number
++++else:
++++++++raise+ValueError("Unexpected+value+type")

a,+b,+c,+d,+e+=+default(5)
f,+g,+h+=+default(3,+False)
i,+j+=+default(2,+"False")
k,+l,+m,+n+=+default(4,+(3,+2,+1))
o,+p+=+default(2,+3.14159265358979)
q,+r,+s+=+default(3,+[1,+2,+3])
t,+u+=+default(2,+{})
v,+w,+x+=+default(3,+DataFrame({'col1':+[7,+13,+42,+73,+666],+'col2':+[1,+0.6,+2,+1.4,+0.3]}))

class+GPU:
++++def+__init__(self,+m,+p):
++++++++self.model+=+m
++++++++self.price+=+p

rtx_3080+=+GPU("RTX+3080",+99999)

y,+z+=+default(2,+rtx_3080)|2683125|entityMap^0|0|0|0|2|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@$I|V|J|W|K|L]]|9|@]|A|$]]|$1|M|3|N|5|6|7|X|8|@]|9|@]|A|$]]|$1|O|3|P|5|D|7|Y|8|@]|9|@]|A|$E|F]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

A mix of previous answers :
<pre><code>from copy import deepcopy

def default(number, value = None):
 if type(value) is dict or object:
 return [deepcopy(value) for _ in range(number)]
 else:
 return [value] * number
 
o, p, q, r, s = default(5)
t, u = default(2, false)
v, w, x = default(3, {})

class GPU:
 def __init__(self, m, p):
 self.model = m
 self.price = p
 
rtx_3080 = GPU(&quot;RTX 3080&quot;, 99999)

y, z = default(2, rtx_3080)
</code></pre>
Edit:
Tried to optimize deepcopy call by better handling mutable variables with pandas/numpy types as well. Might have missed some other ones. If someone find a better way to check for mutability, feel free to share. Althought, this maybe over-engineering whatever your use case is...
<pre><code>import builtins
from copy import deepcopy
from numbers import Number
from pandas import api, DataFrame

mutables = (dict, list, set, DataFrame)
immutables = (str, tuple, frozenset, Number)

def is_built_in_type(var):
 return type(var).__name__ in dir(builtins)

def is_mutable(var):
 return var is not None and (api.types.is_list_like(var) or isinstance(var, mutables) or not is_built_in_type(var))

def is_immutable(var):
 return var is None or isinstance(var, immutables)

def default(number, value=None):
 if is_mutable(value):
 return [deepcopy(value) for _ in range(number)]
 elif is_immutable(value):
 return [value] * number
 else:
 raise ValueError(&quot;Unexpected value type&quot;)

a, b, c, d, e = default(5)
f, g, h = default(3, False)
i, j = default(2, &quot;False&quot;)
k, l, m, n = default(4, (3, 2, 1))
o, p = default(2, 3.14159265358979)
q, r, s = default(3, [1, 2, 3])
t, u = default(2, {})
v, w, x = default(3, DataFrame({'col1': [7, 13, 42, 73, 666], 'col2': [1, 0.6, 2, 1.4, 0.3]}))

class GPU:
 def __init__(self, m, p):
 self.model = m
 self.price = p

rtx_3080 = GPU(&quot;RTX 3080&quot;, 99999)

y, z = default(2, rtx_3080)
</code></pre>

blocks|key|125203|text|在@belgacea的答案下参与了讨论之后，我想发布我认为最好的那个答案的变体：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|125204|import+copy

def+duplicate(value,+n):
++++return+[copy.deepcopy(value)+for+_+in+range(n)]

a,+b,+c+=+duplicate([0],+3)
o,+p,+q,+r,+s+=+duplicate(None,+5)
t,+u+=+duplicate(False,+2)
v,+w,+x+=+duplicate({},+3)
y,+z+=+duplicate(MyClass(),+2)|code-block|syntax|javascript|125205|在所有情况下，deepcopy()都保证可变对象不会在一起初始化的不同变量之间共享，这是要避免的重要陷阱。|offset|length|style|CODE|125206|但我已经将代码简化为最简单的表达式，利用deepcopy已经过了很好的优化，可以在输入不可变的情况下执行浅层复制。我已经用字符串和元组对此进行了测试，如果x是递归不可变的，例如x+=+((1,2),"foo")，那么x+is+copy.deepcopy(x)将返回True，因此尝试避免对不需要深度复制的值调用deepcopy没有任何好处。|125207|我还将函数的签名和名称更改为我认为在使用它的地方可以更好地自文档化的代码。|125208|entityMap^0|0|0|7|A|0|K|8|25|1|2G|H|30|L|4B|8|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@$I|V|J|W|K|L]]|9|@]|A|$]]|$1|M|3|N|5|6|7|X|8|@$I|Y|J|Z|K|L]|$I|10|J|11|K|L]|$I|12|J|13|K|L]|$I|14|J|15|K|L]|$I|16|J|17|K|L]]|9|@]|A|$]]|$1|O|3|P|5|6|7|18|8|@]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|19|8|@]|9|@]|A|$]]]|R|$]]

After having participated in the discussion under @belgacea's answer, I'd like to post the variant of that answer that I think is the best:
<pre class="lang-py prettyprint-override"><code>import copy

def duplicate(value, n):
 return [copy.deepcopy(value) for _ in range(n)]

a, b, c = duplicate([0], 3)
o, p, q, r, s = duplicate(None, 5)
t, u = duplicate(False, 2)
v, w, x = duplicate({}, 3)
y, z = duplicate(MyClass(), 2)
</code></pre>
In all cases, we're guaranteed by <code>deepcopy()</code> that mutable objects are not shared among the different variables initialized together, which is the important gotcha to avoid.
But I've simplified the code to its simplest expression, taking advantage of the fact that <code>deepcopy</code> is already well optimized to do a shallow copy when its input is immutable. I've tested this with strings and tuples, and if <code>x</code> is recursively immutable, e.g., <code>x = ((1,2),&quot;foo&quot;)</code>, then <code>x is copy.deepcopy(x)</code> returns True, so there's no benefit in trying to avoid calling <code>deepcopy</code> on values that don't need a deep copy.
I've also changed the signature and name of the function to something that I think will make better self-documenting code where it is used.

blocks|key|126662|text|这并没有直接回答这个问题，但它是相关的--我使用一个空类的实例来对相似的属性进行分组，因此我不必通过列出所有属性来弄乱我的init方法。|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|126663|class+Empty:
++++pass

class+Application(tk.Frame):
++++def+__init__(self,+master=None):
++++++++super().__init__(master)
++++++++self.w+=+Empty()++++++++++#+widgets
++++++++self.master+=+master
++++++++self.pack()
++++++++self.create_widgets()

++++def+create_widgets(self):
++++++++self.w.entry+=+tk.Entry(self,+bg="orange",+fg="black",+font=FONT)|code-block|syntax|javascript|126664|What+is+the+difference+between+SimpleNamespace+and+empty+class+definition?|126665|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/q/37161275/346711^0|1P|4|0|0|0|22|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|X|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|Y|8|@]|D|@$9|Z|A|10|1|11]]|E|$]]|$1|M|3|-4|5|6|7|12|8|@]|D|@]|E|$]]]|N|$O|$5|P|Q|R|E|$S|T]]]]

This does not directly answer the question, but it is related -- I use an instance of an empty class to group similar attributes, so I do not have to clutter up my init method by listing them all.

<pre><code>class Empty:
 pass

class Application(tk.Frame):
 def __init__(self, master=None):
 super().__init__(master)
 self.w = Empty() # widgets
 self.master = master
 self.pack()
 self.create_widgets()

 def create_widgets(self):
 self.w.entry = tk.Entry(self, bg="orange", fg="black", font=FONT)
</code></pre>

<a href="https://stackoverflow.com/q/37161275/346711">What is the difference between SimpleNamespace and empty class definition?</a>

I have gone through these questions,
<blockquote>
<ol>
<li><a href="https://stackoverflow.com/questions/16348815/python-assigning-multiple-variables-to-same-value-list-behavior">Python assigning multiple variables to same value? list behavior</a>
 concerned with tuples, I want just variables may be a string, integer or dictionary</li>
<li><a href="https://stackoverflow.com/questions/5495332/more-elegant-way-of-declaring-multiple-variables-at-the-same-time">More elegant way of declaring multiple variables at the same time</a>
 The question has something I want to ask, but the accepted answer is much complex</li>
</ol>
</blockquote>
so what I'm trying to achieve,
I declare variables as follows, and I want to reduce these declarations to as less line of code as possible.
<pre><code>details = None
product_base = None
product_identity = None
category_string = None
store_id = None
image_hash = None
image_link_mask = None
results = None
abort = False
data = {}
</code></pre>
What is the simplest, easy to maintain ?

Python initialize multiple variables to the same initial value

我已经看过这些问题了，关于元组，我只希望变量可以是字符串、整数或dictionary这个问题有一些我想问的，但被接受的答案是非常复杂的所以我想要实现的是，我按如下方式声明变量，并希望将这些声明减少到尽可能少的代码行。details = Noneproduct_base = Noneproduct_identity = Nonecategory_string = Nonestore_id = Non

问Python将多个变量初始化为相同的初始值
EN

回答 7

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