Unpacking and increase the values

Question

I am wondering if this is possible somehow. I would like to increase both values once that I unpack it, without having to create two temps variables. Is this somehow possible with multiple assignment and unpacking? I started to try out here:

a, b = 1, 1                                                                                                                                                                           
for i in [1,2,3]: 
  a, b += 1, 1                                                                                                                                                                      

File "<ipython-input-2-a1e761cf8ae1>", line 2
  a, b += 1, 1
  ^
SyntaxError: illegal expression for augmented assignment

for i in [1,2,3]: 
  a, b += (1, 1)                                                                                                                                                                    

File "<ipython-input-3-9317a6e51de4>", line 2
  a, b += (1, 1)
  ^
SyntaxError: illegal expression for augmented assignment

for i in [1,2,3]: 
  (a, b) += (1, 1)                                                                                                                                                                  

File "<ipython-input-4-446db199ce6f>", line 2
  (a, b) += (1, 1)
   ^
SyntaxError: illegal expression for augmented assignment

for i in [1,2,3]: 
  a += 1

But no it isn't. What temporary variables are being created? — Daniel Roseman, Sep 10 '19 at 08:03
Integers are not mutable so Python has to create a new value anyway. — Matthias, Sep 10 '19 at 08:04
@yatu so it is not actually (1,1) but a function which returns a tuple — may, Sep 10 '19 at 08:05
Possible duplicate of [increment int object](https://stackoverflow.com/questions/1135335/increment-int-object) — Chris, Sep 10 '19 at 08:05

chseng · Accepted Answer · 2019-09-10T08:25:49.733

1

maybe map can help you !

a,b =1,1
a,b = map(lambda x,y:x+y, [a,b],[1,1])

map() function returns a map object of the results after applying the given function to each item of a given iterable (list, tuple etc.)

edited Sep 10 '19 at 08:25

answered Sep 10 '19 at 08:10

chseng

116
4

The question is tagged for python 3, not 2. Map does not produce a list – Pynchia Sep 10 '19 at 08:22

score 0 · Answer 2 · edited Sep 10 '19 at 10:14

0

Not exactly what you want, but maybe helpful. Numpy can easily add the values just before you unpack.

import numpy as np

ar = np.array([1,1])
ar +=  1
a,b = ar

yields:

(2,2)

edited Sep 10 '19 at 10:14

sophros

14,672
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answered Sep 10 '19 at 08:14

Christian Sloper

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I do not want to use some external lib – may Sep 10 '19 at 10:10

Unpacking and increase the values

2 Answers2