Naive string search algorithm implementations in Python 2.7

naive_string_search_variations.py

# In the middle of implementing Boyer-Moore's string search algorithm, I decided to play with my original naive search algorithm. It's implemented as an instance method that takes a string to be searched. The object has an attribute 'pattern' which is the pattern to match.

# 1) Here is the original version of the search method, using a double for-loop.
# Makes calls to range and len

def search(self, string):
    for i in range(len(string)):
        for j in range(len(self.pattern)):
            if string[i+j] != self.pattern[j]:
                break
            elif j == len(self.pattern) - 1:
                return i
    return -1

# 2) Here is the second version, using a double while-loop instead.
# Slightly faster, not making calls to range

def search(self, string):
    i = 0
    while i < len(string):
        j = 0
        while j < len(self.pattern) and self.pattern[j] == string[i+j]:
            j += 1
        if j == len(self.pattern):
            return i
        i += 1
    return -1

# 3) Here is the original, replacing range with xrange.
# Faster than both of the previous two.

def search(self, string):
    for i in xrange(len(string)):
        for j in xrange(len(self.pattern)):
            if string[i+j] != self.pattern[j]:
                break
            elif j == len(self.pattern) - 1:
                return i
    return -1
    
# 4) Storing values in local variables = win! With the double while loop, this is the fastest.

def search(self, string):
    len_pat = len(self.pattern)
    len_str = len(string)
    i = 0
    while i < len_str:
        j = 0
        while j < len_pat and self.pattern[j] == string[i+j]:
            j += 1
        if j == len_pat:
            return i
        i += 1
    return -1