Simple code question about lambda and tuples

[JasPyt]

I have a simple code:

my_tuple = (0,1,2,3,4,5,6)
foo = list(filter(lambda x: x-0, my_tuple))

print(foo)

I know what the output is and that it removes the first entry, the 0. I could also change it as follows:

my_tuple = (0,1,2,3,4,5,6)
foo = list(filter(lambda x: x-0 and x-1, my_tuple))

print(foo)

I thought that tuples are immutable? How are the 0 and 1 removed? How does this work and what is this x-0 actually doing?

Yoriz write Oct-03-2021, 02:22 PM:
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[Yoriz]

foo is a list made by using my_tuple, if you print the tuple my_tuple you will find it has not changed.

[ndc85430]

Remember that 0 is treated as false when it is tested for its truth value (see the docs), so x - 0 will evaluate to True for any value that isn't 0. It's a strange way to write that predicate - it would be easier to read written as x != 0, obviously.

[deanhystad]

Or as x not in (0, 1)

[JasPyt]

Remember that 0 is treated as false when it is tested for its truth value (see the docs), so x - 0 will evaluate to True for any value that isn't 0. It's a strange way to write that predicate - it would be easier to read written as x != 0, obviously.

Yes exactly != is what I would have expected. But ok, thanks for the answers!

So the point is:
it starts with x=0 and does the following:
0-0 and 0-1 which is: False and True => gives False
then it continues with the next element in the tuple, the 1:
1-0 and 1-1 which is: True and False => gives False
then 2:
2-0 and 1-1 which is: True and True => gives True

and so on, so that is why 0 and 1 are filtered out. Right?

[buran]

2-0 and 1-1 which is: True and True => gives True

Output:
>>> 2-0 and 1-1
0

0 is False

but I guess you mean

Output:
>>> 2-0 and 2-1
1

[JasPyt]

2-0 and 1-1 which is: True and True => gives True

Output:
>>> 2-0 and 1-1
0

0 is False

but I guess you mean

Output:
>>> 2-0 and 2-1
1

Yes exactly!

[snippsat]

The code is confusing if write like this will most will figure what's going with a quick look.

def number_remove(x: int) -> int:
    if x not in (0, 1):
        return x

my_tuple = (0,1,2,3,4,5,6)
print(list(filter(number_remove, my_tuple)))

Output:
[2, 3, 4, 5, 6]