python csv replace listitem

Question

i have following output from a csv file:

word1|word2|word3|word4|word5|word6|01:12|word8
word1|word2|word3|word4|word5|word6|03:12|word8
word1|word2|word3|word4|word5|word6|01:12|word8

what i need to do is change the time string like this 00:01:12. my idea is to extract the list item [7] and add a "00:" as string to the front.

import csv

with open('temp', 'r') as f:
    reader = csv.reader(f, delimiter="|")
    for row in reader:      
        fixed_time = (str("00:") + row[7])
        begin = row[:6]
        end = row[:8]
        print begin + fixed_time +end

get error message:

TypeError: can only concatenate list (not "str") to list.

i also had a look on this post.

how to change [1,2,3,4] to '1234' using python

i neeed to know if my approach to soloution is the right way. maybe need to use split or anything else for this.

thx for any help

Answer 1

The line that's throwing the exception is

print begin + fixed_time +end

because begin and end are both lists and fixed_time is a string. Whenever you take a slice of a list (that's the row[:6] and row[:8] parts), a list is returned. If you just want to print it out, you can do

print begin, fixed_time, end

and you won't get an error.

Corrected code:

I'm opening a new file for writing (I'm calling it 'final', but you can call it whatever you want), and I'm just writing everything to it with the one modification. It's easiest to just change the one element of the list that has the line (row[6] here), and use '|'.join to write a pipe character between each column.

import csv

with open('temp', 'r') as f, open('final', 'w') as fw:
    reader = csv.reader(f, delimiter="|")
    for row in reader:      
        # just change the element in the row to have the extra zeros
        row[6] = '00:' + row[6]
        # 'write the row back out, separated by | characters, and a new line.
        fw.write('|'.join(row) + '\n')

Answer 2

you can use regex for that:

>>> txt = """\
... word1|word2|word3|word4|word5|word6|01:12|word8
... word1|word2|word3|word4|word5|word6|03:12|word8
... word1|word2|word3|word4|word5|word6|01:12|word8"""

>>> import re
>>> print(re.sub(r'\|(\d\d:\d\d)\|', r'|00:\1|', txt))
word1|word2|word3|word4|word5|word6|00:01:12|word8
word1|word2|word3|word4|word5|word6|00:03:12|word8
word1|word2|word3|word4|word5|word6|00:01:12|word8