Python Syntax Unknown

Question

I just came across an assignment like this in python. I checked everywhere to see what this was but couldn't find it. What does this mean in python?

 total_mask |= is_NA

The operator in the middle is confusing me.

Thanks

Generally speaking, A ?= B is the same as A = A ? B, for most any operator you care to replace the question mark with. — Kevin
– Kevin, Commented Jul 25, 2014 at 18:21
That operator (and many like it) were introduced in PEP 203. — user2555451
– user2555451, Commented Jul 25, 2014 at 18:22

Arusekk · Accepted Answer · 2014-07-25 18:25:05Z

3

It's just an operator of logical OR. If total_mask is

0011101010101001110

and is_NA is

0000000000000100000

then total_mask will become

0011101010101101110

in this case it's just like addition. EDIT: of course the numbers are here written in binary. In Python you can convert a number to a binary string using the bin function, for example

>>> bin(99)
'0b1100011'

answered Jul 25, 2014 at 18:25

Arusekk

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user3874324user3874324 · Accepted Answer · 2014-07-25 18:23:42Z

2

It is the same as

total_mask = total_mask|is_NA

answered Jul 25, 2014 at 18:23

user3874324

2 Comments

fixmycode Over a year ago

@wim care to explain?

wim Over a year ago

consider the case of sets, where this operator means in-place union. the |= operator (which slots into set.__ior__) will preserve the identity of the set, whereas the method you have shown will create a new set. this can have side effects for other references to the same set.

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