Python search and replace not replacing properly

Question

I have this script that needs to replace a file extension and it is not doing so properly:

import os
import sys

#directory is the directory we will work from
directory = "C:\\Users\\joe\\Desktop"
os.chdir(directory)

whatToLookFor = ["Ca", "Cb", "Cd", "Ce", "Cf", "Cg", "Ch", "Ci", "Cj", "Ck", "Cl", "Cm", "Cn", "Co",
                 "Fa", "Fb", "Fc", "Fd", "Fe", "Ff", "Fg", "Fh", "Fi", "Fk", "Fl", "Fm", "Fn", "Fo", 
                 "Fp", "Ga", "Gb", "Gc", "Gd", "Ge", "Gf", "Gg", "Gh", "Gi", "Gj", "Gk", "Gn", "Ja",
                 "Jb", "Jc", "Jd", "Je", "Jf", "Jg", "Jh", "Jk", "Jl", "Jm", "Fj", "cc", "cb", "cd",
                 "ce", "cf", "cg", "ch", "ci", "cj", "ck", "cl", "cm", "cn", "co", "fa", "fb", "fc",
                 "fd", "fe", "ff", "fg", "fh", "fi", "fk", "fl", "fm", "fn", "fo", "fp", "ga", "gb", 
                 "gc", "gd", "ge", "gf", "gg", "gh", "gi", "gj", "gk", "gn", "ja", "jb", "jc", "jd", 
                 "je", "jf", "jg", "jh", "jk", "jl", "jm", "fj"]

oldFile = open("links.htm", "r")
newFile = open("python test.htm", "w")
buffer = oldFile.read()

for item in whatToLookFor:
    for x in range(0, 80):
        if x < 10:
            buffer = buffer.replace(item + str(x), item.upper() + "-0" + str(x))
        else:
            buffer = buffer.replace(item + str(x), item.upper() + "-" + str(x))

newFile.write(buffer)

oldFile.close()
newFile.close()

The file ff10 is being changed to FF-010 when it should not be. It should be changed to FF-10

Please include a sample of your input file ("links.htm"?).

stderr
– stderr

2011-08-19 18:15:45 +00:00
Commented Aug 19, 2011 at 18:15 — stderr
– stderr, Commented Aug 19, 2011 at 18:15

cwallenpoole · Accepted Answer · 2011-08-19 18:18:21Z

2

Without knowing what your actual input is, it will be very difficult to help, however, I did notice one thing. It looks like you are trying to make sure you have two digit numbers in your buffer (after the item from whatToLookFor).

If that's true, life would probably be easier if you replaced this:

if x < 10:
    buffer = buffer.replace(item + str(x), item.upper() + "-0" + str(x))
else:
    buffer = buffer.replace(item + str(x), item.upper() + "-" + str(x))

With:

sx = str(x)
tmp = sx if len(sx) >= 2 else "0" + sx
buffer = buffer.replace(item + sx, item.upper()+ "-" + tmp)

Or, even better:

buffer = buffer.replace(item + str(x), "%s-%02d" % (item.upper(), int(x)) )

edited Aug 19, 2011 at 18:18

answered Aug 19, 2011 at 18:04

cwallenpoole

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Comments

Michael Lorton · Accepted Answer · 2011-08-20 20:45:57Z

1

The file ff10 is being changed to FF-010 when it should not be. It should be changed to FF-10

For some definition of "should". In fact, your code is recognizing the ff1 part and changing it to FF-01. The extra 0 was already in the buffer.

If you like, you can bang your forehead here --> <--

answered Aug 20, 2011 at 20:45

Michael Lorton

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Comments

andronikus · Accepted Answer · 2011-08-19 21:02:14Z

0

Your

if x < 10:

condition is true for 0-9, and false for 10+. That's why you're getting the wrong behavior on #10. Change it to:

if x <= 10:

You'd be surprised how often this happens, to me at least.

answered Aug 19, 2011 at 21:02

andronikus

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1 Comment

Michael Lorton Over a year ago

It's called a "fencepost error" (from the question "if you build a 50-foot fence with one post every five feet, how many posts do you need?" Answer: eleven) and I do it all the time but no, that wasn't the OP's problem.

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