Question

I am trying to change the date format in a text file so that it can be comma-delimited by Year, Month, and Day. Currently, it is in YYYY-MM-DD format and I am trying to replace the hyphens with commas without affecting the other hyphenated text in the file:

2011-1-1,59,44,29,55,42,26,93,80,66,30.15,30.05,29.96,10,8,4,14,3,22,T,7,Rain,201,39.2,76.7,KBWI
2011-1-26,35,34,32,34,31,25,100,82,64,30.04,29.79,29.54,9,2,0,22,11,29,1.82,8,Fog-Rain-Snow-Thunderstorm,23,39.2,76.7,KBWI #I dont want to remove the hyphens for the weather events

A friend told me to use regex with this expression:

re.findall('[\d]{4}-[\d]{1,2}-[\d]{1,2}')

It does find the patterns for all the dates formatted with hyphens, but I have no clue as to how to replace the hyphens with commas for all the lines in the textfile with this match. I’m thinking about creating a new text file with the edited data so that I can use it in another application. Any help would be appreciated.

Answer 1

Without using regexp is simple:

in = open("inputfile", "r")
out = open("outputfile", "w")

for line in in:
    line = line.split(",", 1)
    line[0] = line[0].replace("-", ",")
    out.write(','.join(line))

in.close()
out.close()