Checking if string contains if either of two substring returns true

Question

Results I get for this code is true but the results are false.Checked in atom code editor and online editor

a = "https://www.reddit.com/comments/ado0ym/use_reddit_coins_to_award_gold_to_your_favorite/"
b = "aaaaaaa"
c = "somthing random"

if b or c in a:
    print("true")

else:
    print("false")


# Results return True

in has higher precedence over or, that's all, i.e., you have `if b or (c in a):` — Walter Tross, Jan 25 '19 at 14:04
please try to solve these simple questions yourself, you literally asked a similar question 20 minutes ago --> https://stackoverflow.com/questions/54366507/check-if-the-string-contains-the-substring-returns-true-when-its-actually-false — gold_cy, Jan 25 '19 at 14:05

Talha Israr · Accepted Answer · 2019-01-25T14:20:13.190

4

Python doesnt run this code correctly

 if b or c in a:
    print("true")

The reason is that python percieves this as

 if (b) or (c in a):

And as if b is always True so code doesnt work as expected

This should be

 if (b in a) or (c in a):
    print("true")

Hope it helps

edited Jan 25 '19 at 14:20

answered Jan 25 '19 at 14:05

Talha Israr

654
6
17

Both the strings are not there. B is also false. – am guru prasath Jan 25 '19 at 14:07
No if b checks wheather b is there or not and so if b is always true – Talha Israr Jan 25 '19 at 14:07
@amguruprasath: B isn't false, B is `"use_favorite"`. – RemcoGerlich Jan 25 '19 at 14:08
Yep exactly. :) – Talha Israr Jan 25 '19 at 14:09
""use_favorite"" does not exist in the string please show me it only has ""your_favorite/"" – am guru prasath Jan 25 '19 at 14:10
i would disagree with you . Hope you dont mind @aws – Talha Israr Jan 25 '19 at 14:11
@amguruprasath if you write if b or c in a: python wont check whether b is in a or not it will only check if b exists and it surely does so it always considers this if statement to be True – Talha Israr Jan 25 '19 at 14:13
ok as you say :) – Talha Israr Jan 25 '19 at 14:14
okay now b= "aaaaaaaa" i modified the code now it must be false right? but returns true why ? – am guru prasath Jan 25 '19 at 14:15
@amguruprasath Nope let me explain. The code 'if b or c in a:' is just like 'if (b) or (c in a)' . Note the brackets. The if loop will be true if b is true or c in a is true but when will b be true. Well b will always be true as long as it exists like b="aaaa". . Hope you understand – Talha Israr Jan 25 '19 at 14:17

Stef van der Zon · Answer 2 · 2019-01-25T14:07:46.450

0

The problem with your code is the following:

if b or c in a:
    print("true")

This first checks if b exists. which it does. So it gives True.

What you should do is:

if (b in a) or (c in a):

edited Jan 25 '19 at 14:07

answered Jan 25 '19 at 14:04

Stef van der Zon

633
4
13

No b is not in c that is the problem. Both the strings are not there. – am guru prasath Jan 25 '19 at 14:05
It doesn't even check if c is part of a, as that's not needed if b is truthy. – RemcoGerlich Jan 25 '19 at 14:06
@amguruprasath: but it doesn't check that b is in a; it checks that b evaluated to True-ish, which it does. – RemcoGerlich Jan 25 '19 at 14:07
Both the strings are not there. b is not in a – am guru prasath Jan 25 '19 at 14:07
it doesnt matter if b is in a or not. That's not what you're checking. You're just checking if b exists. – Stef van der Zon Jan 25 '19 at 14:08
"You're just checking if b exists. " but it does not exist and it goes to c to check and it does not exist so the results should be false. – am guru prasath Jan 25 '19 at 14:09
it does exist. b == "use_favorite" – Stef van der Zon Jan 25 '19 at 14:09
""use_favorite"" does not exist in the string please show me it only has ""your_favorite/"" – am guru prasath Jan 25 '19 at 14:11
You declare it at the start. b = "use_favorite". Line 2. In the if statement you're basicly doing: if (b) or (c in a). c is not part of a so that part is false. But if b is true since b is declared and has a value. – Stef van der Zon Jan 25 '19 at 14:12
The problem is that you're never comparing b to a. You're just checking the existance of variable b. – Stef van der Zon Jan 25 '19 at 14:13
@vanderZonStef b is false. That is the problem a has ""your fav"" not use_fav – am guru prasath Jan 25 '19 at 14:13
b is not false. b = "use favorite". Im sorry but really can't explain it any better than this. You should try some basic tutorials about variables and if statements. – Stef van der Zon Jan 25 '19 at 14:14
okay now b= "aaaaaaaa" i modified the code now it must be false right? but returns true why ? – am guru prasath Jan 25 '19 at 14:15
Because b has a different value. The value is "aaaaaaaa". But since it exists it is True. – Stef van der Zon Jan 25 '19 at 14:16

Checking if string contains if either of two substring returns true

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