modify-csv

Apply a user-provided Python function to every cell in one CSV data row, every cell in one column, or one cell. The CSV's first record is treated as its header and is never modified. Row and column indexes are zero-based; columns can also be addressed by their exact header text.

Install

Install a published release from PyPI:

python -m pip install modify-csv

Script contract

The supplied script must define exactly this callable shape:

from typing import Any


def eval(content: Any, row: int, col: int) -> Any:
    return content

Any is provided by Python's standard-library typing module. The function name, parameter names, and three-argument shape are enforced.

content is the current CSV field (initially a string), while row and col are zero-based numeric indexes into the data records and columns. The returned value is passed to Python's CSV writer. The script is ordinary trusted Python and executes with the same permissions as the command.

Examples

Apply a script file to a column selected by header:

modify-csv apply input.csv output.csv --script-file normalize.py --column email

Apply inline code to data row 2:

modify-csv apply input.csv output.csv \
  --script 'def eval(content, row, col): return content.strip()' \
  --row 2

Apply inline code to the cell at data row 0 and column 1:

modify-csv apply input.csv output.csv \
  --script 'def eval(content, row, col): return int(content) * 2' \
  --cell 0 1

Exactly one of --script or --script-file, and exactly one of --row, --column, or --cell, is required. Existing output files are protected; pass --force to replace one.

Generate a ready-to-edit transformation script:

modify-csv template transform.py

Use --force to replace an existing template. Run modify-csv --help or the help for either subcommand to see the required function signature. The original form without the apply subcommand remains supported for compatibility.