How does the adders function work when we add number to the first element?

Asked Dec 07 '18 at 04:19

Active Aug 18 '22 at 06:05

Viewed 102 times

adders = []
for i in [1, 2, 3]:
    add_i = lambda x: x + i
    adders.append(add_i)

adders

[<function __main__.<lambda>>,
 <function __main__.<lambda>>,
 <function __main__.<lambda>>]

If we input add1 = adders[0], then add1 will be x+1. But add1 (5) outputs 8 instead of 6. Why?

edited Dec 07 '18 at 04:33

asked Dec 07 '18 at 04:19

user8314628

1,952
2
22
46

1

Could you provide the code that you use to obtain `8` in this case? – hilberts_drinking_problem Dec 07 '18 at 04:23
Oh sorry, I missed an argument. It should be `add1 = adders[0]`, then `add1(5)` output `8`. – user8314628 Dec 07 '18 at 04:26
This is a problem with `lambda` scopes, as discussed [here](https://stackoverflow.com/questions/938429/scope-of-lambda-functions-and-their-parameters). You can use `lambda x, i=i: x + i` to get the expected behavior. – hilberts_drinking_problem Dec 07 '18 at 04:36
1

Thank you. So I guess the 3 `lambda` functions in my code are the same thing, which is the last one `lambda x: x + 3`. – user8314628 Dec 07 '18 at 04:39
1

They are three distinct function objects doing the same thing. This is different from `adders` containing 3 references to the same function. – hilberts_drinking_problem Dec 07 '18 at 04:40

How does the adders function work when we add number to the first element?

0 Answers0