Multiple increment operators on the same line Python

Question

Is it possible to do multiple variable increments on the same line in Python?

Example:

value1, value2, value3 = 0 value4 = 100 value1, value2, value3 += value4

In my real program I have LOTS of variables that are different but must all be added on with a single variable at one point.

What I am currently doing that I wanted this to replace:

value1 += value4 value2 += value4 value3 += value4 ... value25 += value4

value1, value2, value3 = (v + value4 for v in (value1, value2, value3))... — Delgan
– Delgan, Commented Jan 9, 2016 at 13:22

Mike Müller · Accepted Answer · 2016-01-09 14:01:39Z

8

Tuple and generator unpacking can be useful here:

value1, value2, value3 = 0, 0, 0 value4 = 100 value1, value2, value3 = (value4 + x for x in (value1, value2, value3))

edited Jan 9, 2016 at 14:01

answered Jan 9, 2016 at 13:27

Mike Müller

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2 Comments

Mike Graham Over a year ago

@MikeMüller, that's not tuple unpacking, that's iterable unpacking of a generator expression.

Mike Müller Over a year ago

@MikeGraham Thanks for the pointer. My wording is not totally correct. In the last line no tuple is created. Fixed. I used tuple unpacking for the more general iterable unpacking.

master_Alish · Accepted Answer · 2016-01-09 13:41:20Z

You can create special function for it:

def inc(value, *args): for i in args: yield i+value

And use it:

value1 = value2 = value3 = 0 value4 = 100 value1, value2, value3 = inc(value4, value1, value2, value3)

This is an interesting way to do it, however still very long to type.

Eugene Yarmash · Accepted Answer · 2016-01-09 20:24:39Z

You can update the variables through the dictionary of the current namespace (e.g. vars()):

>>> value1 = value2 = value3 = 0 >>> value4 = 100 >>> for varname in ("value1", "value2", "value3"): ... vars()[varname] += value4 ... >>> value1, value2, value3 (100, 100, 100)

Simon Forsberg · Accepted Answer · 2016-01-09 13:50:55Z

-5

There is an easy way by making a list and looping over it:

value1, value2, value3 = 0 value4 = 100 valuelist = [value1, value2, value3] for x in valuelist: x += value4

edited Jan 9, 2016 at 13:50

Simon Forsberg

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answered Jan 9, 2016 at 13:44

wallabra

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3 Comments

Mike Graham Over a year ago

That doesn't work -- ints are immutable, += rebinds the name, not mutates the value

wallabra Over a year ago

@MikeGraham Then what would be mutable? Maybe converting value1-3 to these mutable values inside the list may work.

Mike Graham Over a year ago

the solution is just not to try to use mutation here, but rather create and assign new values. stackoverflow.com/a/34694027/192839 was a pretty reasonable solution

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