or condition seems to fail in Python3

Question

I have a very long list like this:

old_list = ['cat','dog','bat','cat',...]

I am using the following code to copy this entire list into another with changes for some specific conditions:

new_list = []
for item in old_list:
    if item == ("cat" or "bat"):
        new_list.append("a")
    elif item == "dog" or "fog" or "sog" or "log":
        new_list.append("o")
    else:
        new_list.append(item)

The problem is that in some cases "cat" and "bat" are correctly replaced by "a" but in some cases "cat" or "bat" remains as it is when I print new_list

What am I doing wrong?

You're not comparing item against "fog", "sog" or "log" - you're actually checking if the value as a boolean returns True or False — Alan Kavanagh, Aug 24 '17 at 12:43
You don't have an if before your first elif. And use `if item in ["cat", "bat"]` — Igl3, Aug 24 '17 at 12:45
So close to submitting an answer before this got closed. oh well. You also should change your first `elif` to and `if`. an add an `item ==` after every `or` — Matthew Ciaramitaro, Aug 24 '17 at 12:46
What are you actually trying to accomplish? Can you elaborate more in your question? Right now, it would print things like `["a", "o", "other word"]` — sma, Aug 24 '17 at 12:46
Add your brackets around dog, fog, sog and log like you did in line 3 — Alan Kavanagh, Aug 24 '17 at 12:47
@MatthewCiaramitaro thanks. i made the mistake while typing here. — , Aug 24 '17 at 12:48
Actually, `item == ("cat" or "bat")` seems to be a new variant of the theme, that's evaluated as `item == "cat"` (as `("cat" or "bat")` evaluates as `"cat"`). — tobias_k, Aug 24 '17 at 12:48
you could also do `if item in ["cat,"bat","dog",...]: new_list.append(item[1])` — Matthew Ciaramitaro, Aug 24 '17 at 12:52

score 2 · Accepted Answer · answered Aug 24 '17 at 12:46

2

use

if item in {"dog", "fog", "sog", "log"}:
    ...

answered Aug 24 '17 at 12:46

Finlay McWalter

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score 1 · Answer 2 · answered Aug 24 '17 at 12:47

This will solve your isse

old_list = ['cat','dog','bat','cat']
new_list = []
for item in old_list:
    if item == "cat" or item=="bat":
        new_list.append("a")
    elif item == "dog" or item== "fog" or item=="sog" or item=="log":
        new_list.append("o")
    else:
        new_list.append(item)
print(new_list)

or condition seems to fail in Python3

2 Answers2