# Create 6 column CSV with with added zeros (Solutions w/ perl awk sed) https://stackoverflow.com/a/38106938/120681

fill_csv_columns_with_zeros.bash

  # I have a file.txt containing numbers like
    1, 2, 3
    4, 5
    6, 7, 8, 9,10,11
   12,13,14,15,16
  # I want to create a CSV file by padding each line such that there are 6 values separated by 5 commas, so I need to add to each line an appropriate number of ",0". It shall look like
    1, 2, 3, 0, 0, 0
    4, 5, 0, 0, 0, 0
    6, 7, 8, 9,10,11
   12,13,14,15,16, 0
read -r -d '' SIX_COLUMN_CSV << 'END_SIX_COLUMN_CSV'
  1, 2, 3
  4, 5
  6, 7, 8, 9,10,11
 12,13,14,15,16
END_SIX_COLUMN_CSV
    echo -e "$SIX_COLUMN_CSV" > six_column.csv
  # Solutions:
      perl -lpe '$_ .= ",0" x (5 - tr/,//)'                          six_column.csv
      awk -v FS=, -v OFS=, '{ for(i = NF+1; i <= 6; i++) $i = 0 } 1' six_column.csv
      sed ':b /^\([^,]*,\)\{5\}/ b; { s/$/,0/; b b }'                six_column.csv

read -r -d '' SIX_COLUMN_PY << 'END_SIX_COLUMN_PY'
import sys

max_width = 0
rows = []
for line in sys.stdin:
    line = line.strip()
    existing_vals = line.split(",")
    rows.append(existing_vals)
    max_width = max(max_width, len(existing_vals))

for row in rows:
    zeros_needed = max_width - len(row)
    full_values = row + ["0"] * zeros_needed
    print ",".join(full_values)
END_SIX_COLUMN_PY
    echo -e "$SIX_COLUMN_PY" > six_column.py
    cat six_column.csv | python six_column.py