What is the meaning of following line of python code?

Question

Please elaboarate the following lines of code

def lcs(X , Y):
    # find the length of the strings
    m = len(X)
    n = len(Y)

    l = [[None] * (n + 1) for i in xrange(m + 1)]

Assuming the line you're asking about is the last one, what confuses you? The multiplication on a list? The list comprehension? This is pretty straightforward, if useless, Python code. — Fred Larson
– Fred Larson, Commented Mar 17, 2017 at 15:03
actually it is the part of the solution of longest common subsequence — Divya Rani
– Divya Rani, Commented Mar 18, 2017 at 1:09

thomasborgen · Accepted Answer · 2017-03-17 15:04:45Z

1

I would advise you to adopt ways to figure this out yourself.

edit1: First thing you do is print(l) and see whats up.

This is a pythonesque way of creating arrays:

l = [[None]*(n+1) for i in xrange(m+1)]

and it could be written

l = []
for i in xrange( m + 1 ):
    l.append( [None]*(n+1) )

now its clearer right?

and then you could try to print( [None] * 3 ) to see what this does.

and since the comment says len of strings. then X and Y are strings.

then pass some strings to the function and see what comes out :)

answered Mar 17, 2017 at 15:04

thomasborgen

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