CODEWITHSUNDEEP
python-3.x
user8915882
user8915882

Reputation:

Find characters inside strings from the elements of a list in python

I just started to use python 3. I want to find specific characters inside a string that is part of a list. Here is my code:

num = ["one","two","threex"]
for item in num:
    if item.find("x"):
        print("found")

So, I want to print "found" if the character "x" is inside of one of the elements of the list. But when I run the code, it prints 3 times instead of one.

Why is printing 3 times? Can someone help me?

Upvotes: 4

Views: 7791

Answers (4)

Joe Iddon
Joe Iddon

Reputation: 20414

You need to break out of looping through the strings if 'x' is found as otherwise, it may be found in other strings. Also, when checking if 'x' is in the string, use in instead.

num = ["one","two","threex"]
for item in num:
    if "x" in item:
        print("found")
        break

which outputs:

found

And if I modify the num list so that it has no x in any of the elements:

num = ["one","two","three"]

then there is no output when running the code again.

But why was it printing 3 times before?

Well simply, using item.find("x") will return an integer of the index of 'x' in the string. And the problem with evaluating this with an if-statement is that an integer always evaluates to True unless it is 0. This means that every string in the num list passed the test: if item.find("x") and so for each of the 3 strings, found was printed. In fact, the only time that found wouldn't be printed would be if the string began with an 'x'. In which case, the index of 'x' would be 0 and the if would evaluate to False.

Hope this clears up why your code wasn't working.

Oh, and some examples of testing the if:

>>> if 0:
...     print("yes")
... 
>>> if 1:
...     print("yes")
... 
yes
>>> if -1:
...     print("yes")
... 
yes

Upvotes: 0

Argus Malware
Argus Malware

Reputation: 787

find returns Index if found and -1 otherwise.

num = ["one","two","threex"]
for item in num:
    if item.find("x"):
        print item.find("x")

i hope that you got the solution from above post ,here you know the reason why

Upvotes: 0

meggar
meggar

Reputation: 1219

find() returns -1 if the character is not found in the string. Anything that is not zero is equal to True. try if item.find("x") > -1.

Upvotes: 1

developer_hatch
developer_hatch

Reputation: 16224

You can use in again for strings:

num = ["one","two","threex"]
for item in num:
    if "x" in item:
        print("found")

Think in Strings as a list of chars like "ext" -> ['e', 'x', 't'] so "x" in "extreme" is True

Upvotes: 0

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