Insert standardized Python headers into one or more files.

standard_header.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

"""Insert standardized Python headers into one or more files."""

from __future__ import (absolute_import, print_function)

import io
import re
import sys


def insert_coding_comment(
    path,
    coding_pattern=re.compile("^[ tv]*#.*?coding[:=][ t]*([-_.a-zA-Z0-9]+)"),
    shebang=u"#!/usr/bin/env python\n",
    coding=u"# -*- coding: utf-8 -*-\n"
):
    """
    Insert the shebang and coding comment appropriately into given files.

    Parameters
    ----------
    path : str or path
        The path to the Python module that should be modified.
    coding_pattern : regex
        A compiled regular expression that matches the encoding comment.
    shebang : str
        The shebang to insert if there was one present in the file.
    coding : str
        The encoding comment to insert in the first or second line.
    """
    assert path.endswith(".py")
    with io.open(path, "r") as file_h:
        content = file_h.readlines()
    line_index = 0
    if content[line_index].startswith("#!"):
        content[line_index] = shebang
        line_index += 1
    if coding_pattern.match(content[line_index]):
        content[line_index] = coding
    else:
        content.insert(line_index, coding)
    with io.open(path, "w") as file_h:
        file_h.writelines(content)


def main(files):
    """Insert appropriate headers into one or more Python files."""
    for filename in files:
        try:
            insert_coding_comment(filename)
        except IOError as err:
            print(str(err))
        except IndexError as err:
            print(filename)
            print(str(err))


if __name__ == "__main__":
    main(sys.argv[1:])