Why does the statement if 'a' or 'e' or 'i' or 'o' or 'u' in String: execute even when there are no vowels in string?

Question

My Code:

VowelsInString = False
String = 'bbbb000'
if 'a' or 'e' or 'i' or 'o' or 'u' in String:
  VowelsInString = True
elif 'a' or 'e' or 'i' or 'o' or 'u' not in String:
  VowelsInSting = False

So, I was expecting that when this ran, the if statement would be skipped and the VowelsInString would remain False, but upon running the code, the value of VowelsInString is True.

I expect that I may have done something wrong whilst typing the vowel checker if argument as I am fairly new to the concept of reading characters in strings. I would appreciate if someone would help me on debugging this code.

If that however is not the case, than I would, again, appreciate if someone would help on telling me what I've done wrong.

you could import re and use `if re.search('a|e|i|o|u',string)` — Onyambu, Jul 30 '18 at 19:11
`VowelsInString = any(v in String for v in 'aeiou')` You don't need an `if/elif` for this, it can be done as a one-liner. — David Zemens, Jul 30 '18 at 19:13
@ZeddCodes_ This is one of the most common duplicate questions on Stack Overflow. It's already got plenty of great answers, but it's so easy to answer that lots of people try to write a new answer anyway every time it comes up. — abarnert, Jul 30 '18 at 19:13

Erty Seidohl · Answer 1 · 2018-07-30T19:13:44.763

1

'a' or 'e' or 'i' or 'o' or 'u' in String:

evaluates as

('a') or ('e') or ('i') or ('o') or ('u' in String).

Since 'a' is truthy in python, this evaluates to True.

You can either write

if 'a' in String or 'e' in String ...

or

def has_vowel(String):
    for s in String:
        if s in 'aeiou':
            return True

or perhaps

if any(s in String for s in 'aeiou'):

or (credit to Onyambu):

import re
...
re.search('[aeiou]',string)

edited Jul 30 '18 at 19:13

answered Jul 30 '18 at 19:07

Erty Seidohl

4,487
3
33
45

so instead, i would do if 'a' in String... or 'u' in String? – ZeddCodes_ Jul 30 '18 at 19:08
That's correct. – Erty Seidohl Jul 30 '18 at 19:09
You could also use a loop "the other way": for s in string: if s in ['a', 'e' ...]: return true – Erty Seidohl Jul 30 '18 at 19:09
Alright. Thanks for the answer! – ZeddCodes_ Jul 30 '18 at 19:11
(I can only accept answers after 7 minutes it says) – ZeddCodes_ Jul 30 '18 at 19:11
No prob, glad to help :) – Erty Seidohl Jul 30 '18 at 19:12
Just a query: Did I use 'not' correctly in the elif statement? – ZeddCodes_ Jul 30 '18 at 19:16
@ZeddCodes_ no. For the same reason. Also, since your `if` condition can only be true or false, you don't need to use `elif` (when there are multiple "else" possibilities), or even `else` (which would be OK to use, but unnecessary since this assignment can be done just by evaluating the boolean expression and assigning that value to the `VowelsInString`. – David Zemens Jul 30 '18 at 19:21
You don't need an `if/elif` for this, or even `else`: it can be done in a single expression like: `VowelsInString = any(v in String for v in 'aeiou')` – David Zemens Jul 30 '18 at 19:22

score 0 · Answer 2 · answered Jul 30 '18 at 19:07

0

Your conditions is a tautology:

if 'a':
    print("I am always going to print")

answered Jul 30 '18 at 19:07

Luca Cappelletti

2,485
20
35

score 0 · Answer 3 · answered Jul 30 '18 at 19:07

0

Looks like you are evaluating the character itself as a bool.

It is detecting 'a' as True and returning true.

Try something more like:

if any(i in '<string>' for i in ('a','b','c')):

see: How to check a string for specific characters?

answered Jul 30 '18 at 19:07

Brad Fallon

169
1
7

1

You can just do `for i in 'abc'` here, since strings are iterables of their characters. But, while that might be more readable for experienced Python devs, it might be less readable to novices, so I'm not sure whether the tradeoff is worth it in this case. – abarnert Jul 30 '18 at 19:10

score 0 · Answer 4 · answered Jul 30 '18 at 19:08

0

'a' or 'e' or 'i' or 'o' or 'u' in String is always true. What you meant to do is:

if 'a' in String or 'e' in String or ...:

Or, using any:

if any(c in String for c in 'aeiou'):

answered Jul 30 '18 at 19:08

user2390182

72,016
6
67
89

Why does the statement if 'a' or 'e' or 'i' or 'o' or 'u' in String: execute even when there are no vowels in string?

4 Answers4