cannot write a list of integers, which were made strings to a text file

Question

Hi I'm opening and closing an input and an output file as "infile" and "outfile" and using them in a command line argument to extract specific content from one file to another. However the infile content is a list of integers and as I now know I have to turn them to strings to complete the task...

for lines in infile:
    words=lines.split("\t")
    wated=words[15]
    if wated == "559292":
        dataA.append(str(words[1]))#attempt to write list of integers as strings to file
    outfile.write(dataA+'n')#'+n' apparently needed for this process.

However I keep getting the error:

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

When I try it without the "+'n'":

TypeError: expected a character buffer object

First error is exactly what the error message says; you can't add a list and a string. Second error message: `write` takes a string; you're passing it a list. — Colonel Thirty Two, Dec 11 '15 at 15:02

score 0 · Answer 1 · answered Dec 11 '15 at 15:04

0

Change to this, if you want to store that list in a file:

....
outfile.write(str(dataA)+'n')#'+n' apparently needed for this process.
....

answered Dec 11 '15 at 15:04

admix

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This will technically work but I don't think it's what he really wants because for an input file of N lines, you're outputting a list with 0-to-N elements, N times, for a total of O(N^2). The output file will be a couple megabytes large if the input file is around a kilobyte. – Kevin Dec 11 '15 at 15:08

score 0 · Answer 2 · answered Dec 11 '15 at 15:13

I'm assuming you only want each words[1] value to appear in the output file once, in which case you can do one of these:

don't bother with a list; just write words[1] directly to the file
wait until the end of the loop before writing the list to the file

Your current approach seems to be a mix of the above choices, which is no good. I also assume that when you add "n", you are actually trying to add a newline.

for lines in infile:
  words=lines.split("\t")
  wated=words[15]
  if wated == "559292":
    outfile.write(str(words[1])+'\n')

Or

for lines in infile:
  words=lines.split("\t")
  wated=words[15]
  if wated == "559292":
    dataA.append(str(words[1])+'\n')
outfile.writelines(dataA)

cannot write a list of integers, which were made strings to a text file

2 Answers2