Why does it keep returning false positive?

Question

Why is it that my code keeps returning yes in the code I've written?

def alphaToPhone(alpha):
    for i in range(len(alpha)):
        if i=="b" or "k" or "c":
            phone="yes"
        else:
            phone="no"
    return phone

print(alphaToPhone("23ht"))

! remove `range(len` from `range(len(alpha))`, becouse range(len(alpha)) = [1,2,3,4] for alpha = "23ht" — Denis Kuzin, Jun 21 '17 at 09:19
Because you're short circuiting the `or` operator, the statement `1 == "b" or "k" or "c"` results in `'k'` as the first value is falsey — Jack Evans, Jun 21 '17 at 09:22

mic4ael · Answer 1 · 2017-06-21T09:30:49.483

7

Because non-empty strings evaluate to True in Python. Solution for you problem could be one of the following

if i=="b" or i == "k" or i == "c":

or

if i in ["b", "k", "c"]:

Apart from that you are iterating over a wrong set of values. Replace your for with

for i in alpha:

edited Jun 21 '17 at 09:30

answered Jun 21 '17 at 09:15

mic4ael

7,974
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2

He iterates in range. You are comparing index with letters. – Nurjan Jun 21 '17 at 09:19
Yep, that's wrong too - `for i in alpha:` would be better. – Błotosmętek Jun 21 '17 at 09:28

Arun · Answer 2 · 2017-06-21T09:35:40.467

3

You have missed the check

  def alphaToPhone(alpha):
        for i in alpha:
            if i == "b" or i == "k" or i == "c":
                phone="yes"
            else:
                phone="no"
        return phone

  print(alphaToPhone("23ht"))

edited Jun 21 '17 at 09:35

answered Jun 21 '17 at 09:16

Arun

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He iterates in range. You are comparing index with letters. – Nurjan Jun 21 '17 at 09:21
@Nurzhan: I have updated the answer. – Arun Jun 21 '17 at 09:27

score 2 · Answer 3 · answered Jun 21 '17 at 09:15

2

Your condition i=="b" or "k" or "c" probably isn't what you wanted. It always returns true, because "k" (and "c" as well) is true. What you want is:

if i=="b" or i=="k" or i=="c":

or, better:

if i in {"b", "c", "k"}:

answered Jun 21 '17 at 09:15

Błotosmętek

12,717
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He iterates in range. You are comparing index with letters. – Nurjan Jun 21 '17 at 09:21

score 1 · Answer 4 · answered Jun 21 '17 at 09:17

1

You code should be like this:

def alphaToPhone(alpha):
    for ch in alpha:
        if ch == "b" or ch=="k" or ch=="c":
            phone="yes"
        else:
            phone="no"
    return phone

print(alphaToPhone("23ht"))

answered Jun 21 '17 at 09:17

Nurjan

5,889
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Why does it keep returning false positive?

4 Answers4