问题
I am quite confused, consecutive equal = can be used in python like:
a = b = c
What is this language feature called? Is there something I can read about that?
Can it be generated into 4 equals?
a = b = c = d
回答1:
This is just a way to declare a and b as equal to c.
>>> c=2
>>> a=b=c
>>> a
2
>>> b
2
>>> c
2
So you can use as much as you want:
>>> i=7
>>> a=b=c=d=e=f=g=h=i
You can read more in Multiple Assignment from this Python tutorial.
Python allows you to assign a single value to several variables simultaneously. For example:
a = b = c = 1
Here, an integer object is created with the value 1, and all three variables are assigned to the same memory location. You can also assign multiple objects to multiple variables. For example:
a, b, c = 1, 2, "john"
Here, two integer objects with values 1 and 2 are assigned to variables a and b, and one string object with the value "john" is assigned to the variable c.
There is also another fancy thing! You can swap values like this: a,b=b,a:
>>> a=2
>>> b=5
>>> a,b=b,a
>>> a
5
>>> b
2
回答2:
python support multi variable assignment at a time called multiassignment.
In [188]: a = b = c = d = 4
In [189]: a
Out[189]: 4
In [190]: b
Out[190]: 4
In [191]: c
Out[191]: 4
In [192]: d
Out[192]: 4
In [193]: a = 2
In [194]: b = 2
is same as for immutable object
In [195]: a, b = 2 #int is a immutable object like `tuple`, `str`
while this is not to be mean for mutable object like list, dictionary
read about mutable and immutable
来源：https://stackoverflow.com/questions/27272034/what-is-a-b-c-in-python