Reputation: 37
I am trying to use my Levenshtein algorithm to take one string and compare it to multiple strings in a list or column. The idea is to identify if similar address appear multiple times through out the day. So I would want to pick one address and then run my Levenshtein across multiple strings for the one address. In theory I would rinse and repeat with a different target address.
I've built out a working Levenshtein Model, but am now trying to get it toward my unique situation
import numpy as np
# Define a function that will become the fuzzy match
# I decided to use Levenshtein Distance due to the formulas ability to handle string comparisons of two unique lengths
def string_match(seq1, seq2, ratio_calc = False):
""" levenshtein_ratio_and_distance:
Calculates levenshtein distance between two strings.
If ratio_calc = True, the function computes the
levenshtein distance ratio of similarity between two strings
For all i and j, distance[i,j] will contain the Levenshtein
distance between the first i characters of seq1 and the
first j characters of seq2
"""
# Initialize matrix of zeros
rows = len(seq1)+1
cols = len(seq2)+1
distance = np.zeros((rows,cols),dtype = int)
# Populate matrix of zeros with the indeces of each character of both strings
for i in range(1, rows):
for k in range(1,cols):
distance[i][0] = i
distance[0][k] = k
# loop through the matrix to compute the cost of deletions,insertions and/or substitutions
for col in range(1, cols):
for row in range(1, rows):
if seq1[row-1] == seq2[col-1]:
cost = 0 # If the characters are the same in the two strings in a given position [i,j] then the cost is 0
else:
# In order to align the results with those of the Python Levenshtein package, if we choose to calculate the ratio
# the cost of a substitution is 2. If we calculate just distance, then the cost of a substitution is 1.
if ratio_calc == True:
cost = 2
else:
cost = 1
distance[row][col] = min(distance[row-1][col] + 1, # Cost of deletions
distance[row][col-1] + 1, # Cost of insertions
distance[row-1][col-1] + cost) # Cost of substitutions
if ratio_calc == True:
# Computation of the Levenshtein Distance Ratio
Ratio = round(((len(seq1)+len(seq2)) - distance[row][col]) / (len(seq1)+len(seq2)) * 100, 2)
return "The similarity ratio is {}%".format(Ratio)
else:
# print(distance) # Uncomment if you want to see the matrix showing how the algorithm computes the cost of deletions,
# insertions and/or substitutions
# This is the minimum number of edits needed to convert seq1 to seq2
return "The strings are {} edits away".format(distance[row][col]) ```
seq1 = "8847 N Main St"
seq2 = "9763 Peachtree blvd"
Distance = string_match(seq1, seq2)
ratio = string_match(seq1, seq2, ratio_calc = True)enter code here
print(Distance)
print(ratio)
#Results: the strings are 17 edits away
The similarity ratio is 24.24%
Upvotes: 0
Views: 1058
Reputation: 20568
Looks like you simply want to loop over them:
prev_addrs = [
"8847 N Main St",
"9763 Peachtree blvd",
]
target_addr = '10 Main St.'
for addr in prev_addrs:
distance = string_match(target_addr, addr)
# do something with distance...
BTW, you might find it convenient to return a numeric result rather than a string,
since you'll likely want to compute max( ... )
or compare to threshold or similar.
And do consider pip
installing the package,
https://github.com/ztane/python-Levenshtein/wiki,
since a C extension will have a speed advantage over python loops.
Upvotes: 1