str.find
returns -1
when it does not find the substring.
>>> line = 'hi, this is ABC oh my god!!'
>>> line.find('?')
-1
While str.index
raises ValueError
:
>>> line.index('?')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: substring not found
Both the functions behave the same way if a sub-string is found.
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