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fileinput.py
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"""Helper class to quickly write a loop over all standard input files. Typical use is: import fileinput for line in fileinput.input(): process(line) This iterates over the lines of all files listed in sys.argv[1:], defaulting to sys.stdin if the list is empty. If a filename is '-' it is also replaced by sys.stdin. To specify an alternative list of filenames, pass it as the argument to input(). A single file name is also allowed. Functions filename(), lineno() return the filename and cumulative line number of the line that has just been read; filelineno() returns its line number in the current file; isfirstline() returns true iff the line just read is the first line of its file; isstdin() returns true iff the line was read from sys.stdin. Function nextfile() closes the current file so that the next iteration will read the first line from the next file (if any); lines not read from the file will not count towards the cumulative line count; the filename is not changed until after the first line of the next file has been read. Function close() closes the sequence. Before any lines have been read, filename() returns None and both line numbers are zero; nextfile() has no effect. After all lines have been read, filename() and the line number functions return the values pertaining to the last line read; nextfile() has no effect. All files are opened in text mode by default, you can override this by setting the mode parameter to input() or FileInput.__init__(). If an I/O error occurs during opening or reading a file, the IOError exception is raised. If sys.stdin is used more than once, the second and further use will return no lines, except perhaps for interactive use, or if it has been explicitly reset (e.g. using sys.stdin.seek(0)). Empty files are opened and immediately closed; the only time their presence in the list of filenames is noticeable at all is when the last file opened is empty. It is possible that the last line of a file doesn't end in a newline character; otherwise lines are returned including the trailing newline. Class FileInput is the implementation; its methods filename(), lineno(), fileline(), isfirstline(), isstdin(), nextfile() and close() correspond to the functions in the module. In addition it has a readline() method which returns the next input line, and a __getitem__() method which implements the sequence behavior. The sequence must be accessed in strictly sequential order; sequence access and readline() cannot be mixed. Optional in-place filtering: if the keyword argument inplace=1 is passed to input() or to the FileInput constructor, the file is moved to a backup file and standard output is directed to the input file. This makes it possible to write a filter that rewrites its input file in place. If the keyword argument backup=".<some extension>" is also given, it specifies the extension for the backup file, and the backup file remains around; by default, the extension is ".bak" and it is deleted when the output file is closed. In-place filtering is disabled when standard input is read. XXX The current implementation does not work for MS-DOS 8+3 filesystems. Performance: this module is unfortunately one of the slower ways of processing large numbers of input lines. Nevertheless, a significant speed-up has been obtained by using readlines(bufsize) instead of readline(). A new keyword argument, bufsize=N, is present on the input() function and the FileInput() class to override the default buffer size. XXX Possible additions: - optional getopt argument processing - isatty() - read(), read(size), even readlines() """ import sys, os __all__ = ["input","close","nextfile","filename","lineno","filelineno", "isfirstline","isstdin","FileInput"] _state = None DEFAULT_BUFSIZE = 8*1024 def input(files=None, inplace=0, backup="", bufsize=0, mode="r", openhook=None): """input([files[, inplace[, backup[, mode[, openhook]]]]]) Create an instance of the FileInput class. The instance will be used as global state for the functions of this module, and is also returned to use during iteration. The parameters to this function will be passed along to the constructor of the FileInput class. """ global _state if _state and _state._file: raise RuntimeError, "input() already active" _state = FileInput(files, inplace, backup, bufsize, mode, openhook) return _state def close(): """Close the sequence.""" global _state state = _state _state = None if state: state.close() def nextfile(): """ Close the current file so that the next iteration will read the first line from the next file (if any); lines not read from the file will not count towards the cumulative line count. The filename is not changed until after the first line of the next file has been read. Before the first line has been read, this function has no effect; it cannot be used to skip the first file. After the last line of the last file has been read, this function has no effect. """ if not _state: raise RuntimeError, "no active input()" return _state.nextfile() def filename(): """ Return the name of the file currently being read. Before the first line has been read, returns None. """ if not _state: raise RuntimeError, "no active input()" return _state.filename() def lineno(): """ Return the cumulative line number of the line that has just been read. Before the first line has been read, returns 0. After the last line of the last file has been read, returns the line number of that line. """ if not _state: raise RuntimeError, "no active input()" return _state.lineno() def filelineno(): """ Return the line number in the current file. Before the first line has been read, returns 0. After the last line of the last file has been read, returns the line number of that line within the file. """ if not _state: raise RuntimeError, "no active input()" return _state.filelineno() def fileno(): """ Return the file number of the current file. When no file is currently opened, returns -1. """ if not _state: raise RuntimeError, "no active input()" return _state.fileno() def isfirstline(): """ Returns true the line just read is the first line of its file, otherwise returns false. """ if not _state: raise RuntimeError, "no active input()" return _state.isfirstline() def isstdin(): """ Returns true if the last line was read from sys.stdin, otherwise returns false. """ if not _state: raise RuntimeError, "no active input()" return _state.isstdin() class FileInput: """class FileInput([files[, inplace[, backup[, mode[, openhook]]]]]) Class FileInput is the implementation of the module; its methods filename(), lineno(), fileline(), isfirstline(), isstdin(), fileno(), nextfile() and close() correspond to the functions of the same name in the module. In addition it has a readline() method which returns the next input line, and a __getitem__() method which implements the sequence behavior. The sequence must be accessed in strictly sequential order; random access and readline() cannot be mixed. """ def __init__(self, files=None, inplace=0, backup="", bufsize=0, mode="r", openhook=None): if isinstance(files, basestring): files = (files,) else: if files is None: files = sys.argv[1:] if not files: files = ('-',) else: files = tuple(files) self._files = files self._inplace = inplace self._backup = backup self._bufsize = bufsize or DEFAULT_BUFSIZE self._savestdout = None self._output = None self._filename = None self._lineno = 0 self._filelineno = 0 self._file = None self._isstdin = False self._backupfilename = None self._buffer = [] self._bufindex = 0 # restrict mode argument to reading modes if mode not in ('r', 'rU', 'U', 'rb'): raise ValueError("FileInput opening mode must be one of " "'r', 'rU', 'U' and 'rb'") self._mode = mode if inplace and openhook: raise ValueError("FileInput cannot use an opening hook in inplace mode") elif openhook and not hasattr(openhook, '__call__'): raise ValueError("FileInput openhook must be callable") self._openhook = openhook def __del__(self): self.close() def close(self): self.nextfile() self._files = () def __iter__(self): return self def next(self): try: line = self._buffer[self._bufindex] except IndexError: pass else: self._bufindex += 1 self._lineno += 1 self._filelineno += 1 return line line = self.readline() if not line: raise StopIteration return line def __getitem__(self, i): if i != self._lineno: raise RuntimeError, "accessing lines out of order" try: return self.next() except StopIteration: raise IndexError, "end of input reached" def nextfile(self): savestdout = self._savestdout self._savestdout = 0 if savestdout: sys.stdout = savestdout output = self._output self._output = 0 if output: output.close() file = self._file self._file = 0 if file and not self._isstdin: file.close() backupfilename = self._backupfilename self._backupfilename = 0 if backupfilename and not self._backup: try: os.unlink(backupfilename) except OSError: pass self._isstdin = False self._buffer = [] self._bufindex = 0 def readline(self): try: line = self._buffer[self._bufindex] except IndexError: pass else: self._bufindex += 1 self._lineno += 1 self._filelineno += 1 return line if not self._file: if not self._files: return "" self._filename = self._files[0] self._files = self._files[1:] self._filelineno = 0 self._file = None self._isstdin = False self._backupfilename = 0 if self._filename == '-': self._filename = '<stdin>' self._file = sys.stdin self._isstdin = True else: if self._inplace: self._backupfilename = ( self._filename + (self._backup or os.extsep+"bak")) try: os.unlink(self._backupfilename) except os.error: pass # The next few lines may raise IOError os.rename(self._filename, self._backupfilename) self._file = open(self._backupfilename, self._mode) try: perm = os.fstat(self._file.fileno()).st_mode except OSError: self._output = open(self._filename, "w") else: fd = os.open(self._filename, os.O_CREAT | os.O_WRONLY | os.O_TRUNC, perm) self._output = os.fdopen(fd, "w") try: if hasattr(os, 'chmod'): os.chmod(self._filename, perm) except OSError: pass self._savestdout = sys.stdout sys.stdout = self._output else: # This may raise IOError if self._openhook: self._file = self._openhook(self._filename, self._mode) else: self._file = open(self._filename, self._mode) self._buffer = self._file.readlines(self._bufsize) self._bufindex = 0 if not self._buffer: self.nextfile() # Recursive call return self.readline() def filename(self): return self._filename def lineno(self): return self._lineno def filelineno(self): return self._filelineno def fileno(self): if self._file: try: return self._file.fileno() except ValueError: return -1 else: return -1 def isfirstline(self): return self._filelineno == 1 def isstdin(self): return self._isstdin def hook_compressed(filename, mode): ext = os.path.splitext(filename)[1] if ext == '.gz': import gzip return gzip.open(filename, mode) elif ext == '.bz2': import bz2 return bz2.BZ2File(filename, mode) else: return open(filename, mode) def hook_encoded(encoding): import codecs def openhook(filename, mode): return codecs.open(filename, mode, encoding) return openhook def _test(): import getopt inplace = 0 backup = 0 opts, args = getopt.getopt(sys.argv[1:], "ib:") for o, a in opts: if o == '-i': inplace = 1 if o == '-b': backup = a for line in input(args, inplace=inplace, backup=backup): if line[-1:] == '\n': line = line[:-1] if line[-1:] == '\r': line = line[:-1] print "%d: %s[%d]%s %s" % (lineno(), filename(), filelineno(), isfirstline() and "*" or "", line) print "%d: %s[%d]" % (lineno(), filename(), filelineno()) if __name__ == '__main__': _test()