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I was wondering if the 'find' method on strings was implemented with a linear search, or if python did something more sophisticated. The Python documentation doesn't discuss implementation details, so http://docs.python.org/library/stdtypes.html is of no help. Could someone please point me to the relevant source code?
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Python String find() method returns the lowest index or first occurrence of the substring if it is found in a given string. If it is not found, then it returns -1. Parameters: sub: Substring that needs to be searched in the given string.
Strings can be created by enclosing characters inside a single quote or double-quotes. Even triple quotes can be used in Python but generally used to represent multiline strings and docstrings.
Using the 'in' operator: The in operator is the easiest and pythonic way to check if a python string contains a substring. The in and not in are membership operators, they take in two arguments and evaluate if one is a member of the other. They return a boolean value.
Python Find String in List using count() We can also use count() function to get the number of occurrences of a string in the list. If its output is 0, then it means that string is not present in the list. l1 = ['A', 'B', 'C', 'D', 'A', 'A', 'C'] s = 'A' count = l1.
The comment on the implementation has the following to say:
fast search/count implementation, based on a mix between boyer-moore and horspool, with a few more bells and whistles on the top.
for some more background, see: http://effbot.org/zone/stringlib.htm
—https://github.com/python/cpython/blob/master/Objects/stringlib/fastsearch.h#L5
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You should be able to find it in Objects/stringlib/find.h, although the real code is in fastsearch.h.
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Looks like the algorithm used originates from Boyer-Moore-Horspool algorithm
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