try: # Available in Python 3 from tokenize import open as open_py_source except ImportError: # Copied from python3 tokenize from codecs import lookup, BOM_UTF8 import re from io import TextIOWrapper, open cookie_re = re.compile(r"coding[:=]\s*([-\w.]+)") def _get_normal_name(orig_enc): """Imitates get_normal_name in tokenizer.c.""" # Only care about the first 12 characters. enc = orig_enc[:12].lower().replace("_", "-") if enc == "utf-8" or enc.startswith("utf-8-"): return "utf-8" if enc in ("latin-1", "iso-8859-1", "iso-latin-1") or \ enc.startswith(("latin-1-", "iso-8859-1-", "iso-latin-1-")): return "iso-8859-1" return orig_enc def _detect_encoding(readline): """ The detect_encoding() function is used to detect the encoding that should be used to decode a Python source file. It requires one argment, readline, in the same way as the tokenize() generator. It will call readline a maximum of twice, and return the encoding used (as a string) and a list of any lines (left as bytes) it has read in. It detects the encoding from the presence of a utf-8 bom or an encoding cookie as specified in pep-0263. If both a bom and a cookie are present, but disagree, a SyntaxError will be raised. If the encoding cookie is an invalid charset, raise a SyntaxError. Note that if a utf-8 bom is found, 'utf-8-sig' is returned. If no encoding is specified, then the default of 'utf-8' will be returned. """ bom_found = False encoding = None default = 'utf-8' def read_or_stop(): try: return readline() except StopIteration: return b'' def find_cookie(line): try: line_string = line.decode('ascii') except UnicodeDecodeError: return None matches = cookie_re.findall(line_string) if not matches: return None encoding = _get_normal_name(matches[0]) try: codec = lookup(encoding) except LookupError: # This behaviour mimics the Python interpreter raise SyntaxError("unknown encoding: " + encoding) if bom_found: if codec.name != 'utf-8': # This behaviour mimics the Python interpreter raise SyntaxError('encoding problem: utf-8') encoding += '-sig' return encoding first = read_or_stop() if first.startswith(BOM_UTF8): bom_found = True first = first[3:] default = 'utf-8-sig' if not first: return default, [] encoding = find_cookie(first) if encoding: return encoding, [first] second = read_or_stop() if not second: return default, [first] encoding = find_cookie(second) if encoding: return encoding, [first, second] return default, [first, second] def open_py_source(filename): """Open a file in read only mode using the encoding detected by detect_encoding(). """ buffer = open(filename, 'rb') encoding, lines = _detect_encoding(buffer.readline) buffer.seek(0) text = TextIOWrapper(buffer, encoding, line_buffering=True) text.mode = 'r' return text