tools/misc_utils.py

# Copyright 2014 Google Inc.
#
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.


"""Miscellaneous utilities."""


import re


class ReSearch(object):
    """A collection of static methods for regexing things."""

    @staticmethod
    def search_within_stream(input_stream, pattern, default=None):
        """Search for regular expression in a file-like object.

        Opens a file for reading and searches line by line for a match to
        the regex and returns the parenthesized group named return for the
        first match.  Does not search across newlines.

        For example:
            pattern = '^root(:[^:]*){4}:(?P<return>[^:]*)'
            with open('/etc/passwd', 'r') as stream:
                return search_within_file(stream, pattern)
        should return root's home directory (/root on my system).

        Args:
            input_stream: file-like object to be read
            pattern: (string) to be passed to re.compile
            default: what to return if no match

        Returns:
            A string or whatever default is
        """
        pattern_object = re.compile(pattern)
        for line in input_stream:
            match = pattern_object.search(line)
            if match:
                return match.group('return')
        return default

    @staticmethod
    def search_within_string(input_string, pattern, default=None):
        """Search for regular expression in a string.

        Args:
            input_string: (string) to be searched
            pattern: (string) to be passed to re.compile
            default: what to return if no match

        Returns:
            A string or whatever default is
        """
        match = re.search(pattern, input_string)
        return match.group('return') if match else default