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# String manipulation
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import codecs
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import re
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import util
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##### Parsing
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def split(sep, str_):
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    '''Returns [] if str_ == ""'''
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    if str_ == '': return []
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    else: return str_.split(sep)
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def remove_prefix(prefix, str_):
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    if str_.startswith(prefix): return str_[len(prefix):]
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    else: return str_
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def remove_prefixes(prefixes, str_):
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    for prefix in prefixes: str_ = remove_prefix(prefix, str_)
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    return str_
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def with_prefixes(prefixes, str_): return (p+str_ for p in prefixes)
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def remove_suffix(suffix, str_):
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    if str_.endswith(suffix): return str_[:-len(suffix)]
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    else: return str_
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def overlaps(str0, str1): return str0.find(str1) >= 0 or str1.find(str0) >= 0
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##### Unicode
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unicode_reader = codecs.getreader('utf_8')
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def to_unicode(str_):
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    if isinstance(str_, unicode): return str_
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    encodings = ['utf_8', 'latin_1']
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    for encoding in encodings:
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        try: return unicode(str_, encoding)
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        except UnicodeDecodeError, e: pass
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    raise AssertionError(encoding+' is not a catch-all encoding')
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def ustr(val):
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    '''Like built-in str() but converts to unicode object'''
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    if not util.is_str(val): val = str(val)
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    return to_unicode(val)
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##### Line endings
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def extract_line_ending(line):
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    '''@return tuple (contents, ending)'''
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    contents = remove_suffix('\r', remove_suffix('\n', line))
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    return (contents, line[len(contents):])
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def remove_line_ending(line): return extract_line_ending(line)[0]
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def ensure_newl(str_): return remove_line_ending(str_)+'\n'
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def is_multiline(str_):
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    newl_idx = str_.find('\n')
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    return newl_idx >= 0 and newl_idx != len(str_)-1 # has newline before end
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def remove_extra_newl(str_):
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    if is_multiline(str_): return str_
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    else: return str_.rstrip()
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def std_newl(str_): return str_.replace('\r\n', '\n').replace('\r', '\n')
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##### Whitespace
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def cleanup(str_): return std_newl(str_.strip())
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def single_space(str_): return re.sub(r' {2,}', r' ', str_.strip())
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def one_line(str_): return re.sub(r'\n *', r' ', cleanup(str_))
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##### Control characters
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def is_ctrl(char):
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    '''Whether char is a (non-printable) control character'''
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    return ord(char) < 32 and not char.isspace()
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def strip_ctrl(str_):
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    '''Strips (non-printable) control characters'''
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    return ''.join(filter(lambda c: not is_ctrl(c), str_))
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