Adding a comma to end of first row of csv files within a directory using python-CodePudding

Ive got some code that lets me open all csv files in a directory and run through them removing the top 2 lines of each file, Ideally during this process I would like it to also add a single comma at the end of the new first line (what would have been originally line 3)

Another approach that's possible could be to remove the trailing comma's on all other rows that appear in each of the csvs.

Any thoughts or approaches would be gratefully received.

import glob

path='P:\pytest'
for filename in glob.iglob(path '/*.csv'):
  with open(filename, 'r') as f:
    lines = f.read().split("\n")
    f.close()
    if len(lines) >= 1:
      lines = lines[2:]
      o = open(filename, 'w')
      for line in lines:
        o.write(line '\n')
      o.close()

CodePudding user response：

adding a counter in there can solve this:

import glob

path=r'C:/Users/dsqallihoussaini/Desktop/dev_projects/stack_over_flow'
for filename in glob.iglob(path '/*.csv'):
  with open(filename, 'r') as f:
    lines = f.read().split("\n")
    print(lines)
    f.close()
    if len(lines) >= 1:
      lines = lines[2:]
      o = open(filename, 'w')
      counter=0
      for line in lines:
        counter=counter 1
        if counter==1:
            o.write(line ',\n')
        else:
            o.write(line '\n')
      o.close()

CodePudding user response：

One possible problem with your code is that you are reading the whole file into memory, which might be fine. If you are reading larger files, then you want to process the file line by line.

The easiest way to do that is to use the fileinput module: https://docs.python.org/3/library/fileinput.html

Something like the following should work:

#!/usr/bin/env python3

import glob
import fileinput

# inplace makes a backup of the file, then any output to stdout is written 
# to the current file.
# change the glob..below is just an example.
#
# Iterate through each file in the glob.iglob() results
with fileinput.input(files=glob.iglob('*.csv'), inplace=True) as f:
    for line in f:              # Iterate over each line of the current file.
        if f.filelineno() > 2:  # Skip the first two lines
            # Note: 'line' has the newline in it.
            # Insert the comma if line 3 of the file, otherwise output original line
            print(line[:-1] ',') if f.filelineno() == 3 else print(line, end="")