| """New I/O library. |
| |
| This is an early prototype; eventually some of this will be |
| reimplemented in C and the rest may be turned into a package. |
| |
| See PEP 3116. |
| |
| XXX need to default buffer size to 1 if isatty() |
| XXX need to support 1 meaning line-buffered |
| XXX change behavior of blocking I/O |
| XXX don't use assert to validate input requirements |
| """ |
| |
| __author__ = ("Guido van Rossum <guido@python.org>, " |
| "Mike Verdone <mike.verdone@gmail.com>, " |
| "Mark Russell <mark.russell@zen.co.uk>") |
| |
| __all__ = ["open", "RawIOBase", "FileIO", "SocketIO", "BytesIO", |
| "BufferedReader", "BufferedWriter", "BufferedRWPair", |
| "BufferedRandom"] |
| |
| import os |
| import sys |
| import codecs |
| import warnings |
| |
| DEFAULT_BUFFER_SIZE = 8 * 1024 # bytes |
| DEFAULT_MAX_BUFFER_SIZE = 16 * 1024 # bytes |
| |
| |
| class BlockingIO(IOError): |
| |
| def __init__(self, errno, strerror, characters_written): |
| IOError.__init__(self, errno, strerror) |
| self.characters_written = characters_written |
| |
| |
| def open(filename, mode="r", buffering=None, *, encoding=None): |
| """Replacement for the built-in open function. |
| |
| Args: |
| filename: string giving the name of the file to be opened |
| mode: optional mode string; see below |
| buffering: optional int >= 0 giving the buffer size; values |
| can be: 0 = unbuffered, 1 = line buffered, |
| larger = fully buffered |
| encoding: optional string giving the text encoding (*must* be given |
| as a keyword argument) |
| |
| Mode strings characters: |
| 'r': open for reading (default) |
| 'w': open for writing, truncating the file first |
| 'a': open for writing, appending to the end if the file exists |
| 'b': binary mode |
| 't': text mode (default) |
| '+': open a disk file for updating (implies reading and writing) |
| 'U': universal newline mode (for backwards compatibility) |
| |
| Constraints: |
| - encoding must not be given when a binary mode is given |
| - buffering must not be zero when a text mode is given |
| |
| Returns: |
| Depending on the mode and buffering arguments, either a raw |
| binary stream, a buffered binary stream, or a buffered text |
| stream, open for reading and/or writing. |
| """ |
| assert isinstance(filename, basestring) |
| assert isinstance(mode, basestring) |
| assert buffering is None or isinstance(buffering, int) |
| assert encoding is None or isinstance(encoding, basestring) |
| modes = set(mode) |
| if modes - set("arwb+tU") or len(mode) > len(modes): |
| raise ValueError("invalid mode: %r" % mode) |
| reading = "r" in modes |
| writing = "w" in modes |
| appending = "a" in modes |
| updating = "+" in modes |
| text = "t" in modes |
| binary = "b" in modes |
| if not reading and not writing and not appending and "U" in modes: |
| reading = True |
| if text and binary: |
| raise ValueError("can't have text and binary mode at once") |
| if reading + writing + appending > 1: |
| raise ValueError("can't have read/write/append mode at once") |
| if not (reading or writing or appending): |
| raise ValueError("must have exactly one of read/write/append mode") |
| if binary and encoding is not None: |
| raise ValueError("binary mode doesn't take an encoding") |
| raw = FileIO(filename, |
| (reading and "r" or "") + |
| (writing and "w" or "") + |
| (appending and "a" or "") + |
| (updating and "+" or "")) |
| if buffering is None: |
| buffering = DEFAULT_BUFFER_SIZE |
| # XXX Should default to line buffering if os.isatty(raw.fileno()) |
| try: |
| bs = os.fstat(raw.fileno()).st_blksize |
| except (os.error, AttributeError): |
| pass |
| else: |
| if bs > 1: |
| buffering = bs |
| if buffering < 0: |
| raise ValueError("invalid buffering size") |
| if buffering == 0: |
| if binary: |
| return raw |
| raise ValueError("can't have unbuffered text I/O") |
| if updating: |
| buffer = BufferedRandom(raw, buffering) |
| elif writing or appending: |
| buffer = BufferedWriter(raw, buffering) |
| else: |
| assert reading |
| buffer = BufferedReader(raw, buffering) |
| if binary: |
| return buffer |
| # XXX What about newline conventions? |
| textio = TextIOWrapper(buffer, encoding) |
| return textio |
| |
| |
| class RawIOBase: |
| |
| """Base class for raw binary I/O. |
| |
| This class provides dummy implementations for all methods that |
| derived classes can override selectively; the default |
| implementations represent a file that cannot be read, written or |
| seeked. |
| |
| The read() method is implemented by calling readinto(); derived |
| classes that want to support read() only need to implement |
| readinto() as a primitive operation. |
| """ |
| |
| def read(self, n): |
| """read(n: int) -> bytes. Read and return up to n bytes. |
| |
| Returns an empty bytes array on EOF, or None if the object is |
| set not to block and has no data to read. |
| """ |
| b = bytes(n.__index__()) |
| n = self.readinto(b) |
| del b[n:] |
| return b |
| |
| def readinto(self, b): |
| """readinto(b: bytes) -> None. Read up to len(b) bytes into b. |
| |
| Returns number of bytes read (0 for EOF), or None if the object |
| is set not to block as has no data to read. |
| """ |
| raise IOError(".readinto() not supported") |
| |
| def write(self, b): |
| """write(b: bytes) -> int. Write the given buffer to the IO stream. |
| |
| Returns the number of bytes written, which may be less than len(b). |
| """ |
| raise IOError(".write() not supported") |
| |
| def seek(self, pos, whence=0): |
| """seek(pos: int, whence: int = 0) -> None. Change stream position. |
| |
| Seek to byte offset pos relative to position indicated by whence: |
| 0 Start of stream (the default). pos should be >= 0; |
| 1 Current position - whence may be negative; |
| 2 End of stream - whence usually negative. |
| """ |
| raise IOError(".seek() not supported") |
| |
| def tell(self): |
| """tell() -> int. Return current stream position.""" |
| raise IOError(".tell() not supported") |
| |
| def truncate(self, pos=None): |
| """truncate(size: int = None) -> None. Truncate file to size bytes. |
| |
| Size defaults to the current IO position as reported by tell(). |
| """ |
| raise IOError(".truncate() not supported") |
| |
| def close(self): |
| """close() -> None. Close IO object.""" |
| pass |
| |
| def seekable(self): |
| """seekable() -> bool. Return whether object supports random access. |
| |
| If False, seek(), tell() and truncate() will raise IOError. |
| This method may need to do a test seek(). |
| """ |
| return False |
| |
| def readable(self): |
| """readable() -> bool. Return whether object was opened for reading. |
| |
| If False, read() will raise IOError. |
| """ |
| return False |
| |
| def writable(self): |
| """writable() -> bool. Return whether object was opened for writing. |
| |
| If False, write() and truncate() will raise IOError. |
| """ |
| return False |
| |
| def __enter__(self): |
| """Context management protocol. Returns self.""" |
| return self |
| |
| def __exit__(self, *args): |
| """Context management protocol. Same as close()""" |
| self.close() |
| |
| def fileno(self): |
| """fileno() -> int. Return underlying file descriptor if there is one. |
| |
| Raises IOError if the IO object does not use a file descriptor. |
| """ |
| raise IOError(".fileno() not supported") |
| |
| |
| class _PyFileIO(RawIOBase): |
| |
| """Raw I/O implementation for OS files.""" |
| |
| # XXX More docs |
| |
| def __init__(self, filename, mode): |
| self._seekable = None |
| self._mode = mode |
| if mode == "r": |
| flags = os.O_RDONLY |
| elif mode == "w": |
| flags = os.O_WRONLY | os.O_CREAT | os.O_TRUNC |
| elif mode == "r+": |
| flags = os.O_RDWR |
| else: |
| assert 0, "unsupported mode %r (for now)" % mode |
| if hasattr(os, "O_BINARY"): |
| flags |= os.O_BINARY |
| self._fd = os.open(filename, flags) |
| |
| def readinto(self, b): |
| # XXX We really should have os.readinto() |
| tmp = os.read(self._fd, len(b)) |
| n = len(tmp) |
| b[:n] = tmp |
| return n |
| |
| def write(self, b): |
| return os.write(self._fd, b) |
| |
| def seek(self, pos, whence=0): |
| os.lseek(self._fd, pos, whence) |
| |
| def tell(self): |
| return os.lseek(self._fd, 0, 1) |
| |
| def truncate(self, pos=None): |
| if pos is None: |
| pos = self.tell() |
| os.ftruncate(self._fd, pos) |
| |
| def close(self): |
| # Must be idempotent |
| # XXX But what about thread-safe? |
| fd = self._fd |
| self._fd = -1 |
| if fd >= 0: |
| os.close(fd) |
| |
| def readable(self): |
| return "r" in self._mode or "+" in self._mode |
| |
| def writable(self): |
| return "w" in self._mode or "+" in self._mode or "a" in self._mode |
| |
| def seekable(self): |
| if self._seekable is None: |
| try: |
| os.lseek(self._fd, 0, 1) |
| except os.error: |
| self._seekable = False |
| else: |
| self._seekable = True |
| return self._seekable |
| |
| def fileno(self): |
| return self._fd |
| |
| |
| try: |
| import _fileio |
| except ImportError: |
| # Let's use the Python version |
| warnings.warn("Can't import _fileio, using slower Python lookalike", |
| RuntimeWarning) |
| FileIO = _PyFileIO |
| else: |
| # Create a trivial subclass with the proper inheritance structure |
| class FileIO(_fileio._FileIO, RawIOBase): |
| """Raw I/O implementation for OS files.""" |
| # XXX More docs |
| |
| |
| class SocketIO(RawIOBase): |
| |
| """Raw I/O implementation for stream sockets.""" |
| |
| # XXX More docs |
| |
| def __init__(self, sock, mode): |
| assert mode in ("r", "w", "rw") |
| self._sock = sock |
| self._mode = mode |
| |
| def readinto(self, b): |
| return self._sock.recv_into(b) |
| |
| def write(self, b): |
| return self._sock.send(b) |
| |
| def close(self): |
| self._sock.close() |
| |
| def readable(self): |
| return "r" in self._mode |
| |
| def writable(self): |
| return "w" in self._mode |
| |
| def fileno(self): |
| return self._sock.fileno() |
| |
| |
| class _MemoryIOBase(RawIOBase): |
| |
| # XXX docstring |
| |
| def __init__(self, buffer): |
| self._buffer = buffer |
| self._pos = 0 |
| |
| def getvalue(self): |
| return self._buffer |
| |
| def read(self, n=None): |
| if n is None: |
| n = len(self._buffer) |
| assert n >= 0 |
| newpos = min(len(self._buffer), self._pos + n) |
| b = self._buffer[self._pos : newpos] |
| self._pos = newpos |
| return b |
| |
| def readinto(self, b): |
| tmp = self.read(len(b)) |
| n = len(tmp) |
| b[:n] = tmp |
| return n |
| |
| def write(self, b): |
| n = len(b) |
| newpos = self._pos + n |
| self._buffer[self._pos:newpos] = b |
| self._pos = newpos |
| return n |
| |
| def seek(self, pos, whence=0): |
| if whence == 0: |
| self._pos = max(0, pos) |
| elif whence == 1: |
| self._pos = max(0, self._pos + pos) |
| elif whence == 2: |
| self._pos = max(0, len(self._buffer) + pos) |
| else: |
| raise IOError("invalid whence value") |
| |
| def tell(self): |
| return self._pos |
| |
| def truncate(self, pos=None): |
| if pos is None: |
| pos = self._pos |
| else: |
| self._pos = max(0, pos) |
| del self._buffer[pos:] |
| |
| def readable(self): |
| return True |
| |
| def writable(self): |
| return True |
| |
| def seekable(self): |
| return True |
| |
| |
| class BytesIO(_MemoryIOBase): |
| |
| """Buffered I/O implementation using a bytes buffer, like StringIO.""" |
| |
| # XXX More docs |
| |
| def __init__(self, inital_bytes=None): |
| buffer = b"" |
| if inital_bytes is not None: |
| buffer += inital_bytes |
| _MemoryIOBase.__init__(self, buffer) |
| |
| |
| class StringIO(_MemoryIOBase): |
| |
| """Buffered I/O implementation using a string buffer, like StringIO.""" |
| |
| # XXX More docs |
| |
| # XXX Reuses the same code as BytesIO, just with a string rather |
| # that bytes as the _buffer value. That won't work in C of course. |
| |
| def __init__(self, inital_string=None): |
| buffer = "" |
| if inital_string is not None: |
| buffer += inital_string |
| _MemoryIOBase.__init__(self, buffer) |
| |
| |
| class BufferedIOBase(RawIOBase): |
| |
| """Base class for buffered IO objects.""" |
| |
| def flush(self): |
| """Flush the buffer to the underlying raw IO object.""" |
| raise IOError(".flush() unsupported") |
| |
| def seekable(self): |
| return self.raw.seekable() |
| |
| |
| class BufferedReader(BufferedIOBase): |
| |
| """Buffer for a readable sequential RawIO object. |
| |
| Does not allow random access (seek, tell). |
| """ |
| |
| def __init__(self, raw, buffer_size=DEFAULT_BUFFER_SIZE): |
| """Create a new buffered reader using the given readable raw IO object. |
| """ |
| assert raw.readable() |
| self.raw = raw |
| self._read_buf = b"" |
| self.buffer_size = buffer_size |
| if hasattr(raw, 'fileno'): |
| self.fileno = raw.fileno |
| |
| def read(self, n=None): |
| """Read n bytes. |
| |
| Returns exactly n bytes of data unless the underlying raw IO |
| stream reaches EOF of if the call would block in non-blocking |
| mode. If n is None, read until EOF or until read() would |
| block. |
| """ |
| # XXX n == 0 should return b""? n < 0 should be the same as n is None? |
| assert n is None or n > 0, '.read(): Bad read size %r' % n |
| nodata_val = b"" |
| while n is None or len(self._read_buf) < n: |
| to_read = max(self.buffer_size, |
| n if n is not None else 2*len(self._read_buf)) |
| current = self.raw.read(to_read) |
| |
| if current in (b"", None): |
| nodata_val = current |
| break |
| self._read_buf += current |
| if self._read_buf: |
| if n is None: |
| n = len(self._read_buf) |
| out = self._read_buf[:n] |
| self._read_buf = self._read_buf[n:] |
| else: |
| out = nodata_val |
| return out |
| |
| def readable(self): |
| return True |
| |
| def fileno(self): |
| return self.raw.fileno() |
| |
| def flush(self): |
| # Flush is a no-op |
| pass |
| |
| def tell(self): |
| return self.raw.tell() - len(self._read_buf) |
| |
| def seek(self, pos, whence=0): |
| if whence == 1: |
| pos -= len(self._read_buf) |
| self.raw.seek(pos, whence) |
| self._read_buf = b"" |
| |
| def close(self): |
| self.raw.close() |
| |
| |
| class BufferedWriter(BufferedIOBase): |
| |
| # XXX docstring |
| |
| def __init__(self, raw, buffer_size=DEFAULT_BUFFER_SIZE, |
| max_buffer_size=DEFAULT_MAX_BUFFER_SIZE): |
| assert raw.writable() |
| self.raw = raw |
| self.buffer_size = buffer_size |
| self.max_buffer_size = max_buffer_size |
| self._write_buf = b"" |
| |
| def write(self, b): |
| # XXX we can implement some more tricks to try and avoid partial writes |
| assert issubclass(type(b), bytes) |
| if len(self._write_buf) > self.buffer_size: |
| # We're full, so let's pre-flush the buffer |
| try: |
| self.flush() |
| except BlockingIO as e: |
| # We can't accept anything else. |
| # XXX Why not just let the exception pass through? |
| raise BlockingIO(e.errno, e.strerror, 0) |
| self._write_buf += b |
| if len(self._write_buf) > self.buffer_size: |
| try: |
| self.flush() |
| except BlockingIO as e: |
| if (len(self._write_buf) > self.max_buffer_size): |
| # We've hit max_buffer_size. We have to accept a partial |
| # write and cut back our buffer. |
| overage = len(self._write_buf) - self.max_buffer_size |
| self._write_buf = self._write_buf[:self.max_buffer_size] |
| raise BlockingIO(e.errno, e.strerror, overage) |
| |
| def writable(self): |
| return True |
| |
| def flush(self): |
| written = 0 |
| try: |
| while self._write_buf: |
| n = self.raw.write(self._write_buf) |
| del self._write_buf[:n] |
| written += n |
| except BlockingIO as e: |
| n = e.characters_written |
| del self._write_buf[:n] |
| written += n |
| raise BlockingIO(e.errno, e.strerror, written) |
| |
| def tell(self): |
| return self.raw.tell() + len(self._write_buf) |
| |
| def seek(self, pos, whence=0): |
| self.flush() |
| self.raw.seek(pos, whence) |
| |
| def fileno(self): |
| return self.raw.fileno() |
| |
| def close(self): |
| self.flush() |
| self.raw.close() |
| |
| def __del__(self): |
| self.close() |
| |
| |
| class BufferedRWPair(BufferedReader, BufferedWriter): |
| |
| """A buffered reader and writer object together. |
| |
| A buffered reader object and buffered writer object put together to |
| form a sequential IO object that can read and write. |
| |
| This is typically used with a socket or two-way pipe. |
| """ |
| |
| def __init__(self, reader, writer, buffer_size=DEFAULT_BUFFER_SIZE, |
| max_buffer_size=DEFAULT_MAX_BUFFER_SIZE): |
| assert reader.readable() |
| assert writer.writable() |
| BufferedReader.__init__(self, reader) |
| BufferedWriter.__init__(self, writer, buffer_size, max_buffer_size) |
| self.reader = reader |
| self.writer = writer |
| |
| def read(self, n=None): |
| return self.reader.read(n) |
| |
| def write(self, b): |
| return self.writer.write(b) |
| |
| def readable(self): |
| return self.reader.readable() |
| |
| def writable(self): |
| return self.writer.writable() |
| |
| def flush(self): |
| return self.writer.flush() |
| |
| def seekable(self): |
| return False |
| |
| def fileno(self): |
| # XXX whose fileno do we return? Reader's? Writer's? Unsupported? |
| raise IOError(".fileno() unsupported") |
| |
| def close(self): |
| self.reader.close() |
| self.writer.close() |
| |
| |
| class BufferedRandom(BufferedReader, BufferedWriter): |
| |
| # XXX docstring |
| |
| def __init__(self, raw, buffer_size=DEFAULT_BUFFER_SIZE, |
| max_buffer_size=DEFAULT_MAX_BUFFER_SIZE): |
| assert raw.seekable() |
| BufferedReader.__init__(self, raw) |
| BufferedWriter.__init__(self, raw, buffer_size, max_buffer_size) |
| |
| def readable(self): |
| return self.raw.readable() |
| |
| def writable(self): |
| return self.raw.writable() |
| |
| def seek(self, pos, whence=0): |
| self.flush() |
| # First do the raw seek, then empty the read buffer, so that |
| # if the raw seek fails, we don't lose buffered data forever. |
| self.raw.seek(pos, whence) |
| self._read_buf = b"" |
| # XXX I suppose we could implement some magic here to move through the |
| # existing read buffer in the case of seek(<some small +ve number>, 1) |
| # XXX OTOH it might be good to *guarantee* that the buffer is |
| # empty after a seek or flush; for small relative forward |
| # seeks one might as well use small reads instead. |
| |
| def tell(self): |
| if (self._write_buf): |
| return self.raw.tell() + len(self._write_buf) |
| else: |
| return self.raw.tell() - len(self._read_buf) |
| |
| def read(self, n=None): |
| self.flush() |
| return BufferedReader.read(self, n) |
| |
| def write(self, b): |
| if self._read_buf: |
| self.raw.seek(-len(self._read_buf), 1) # Undo readahead |
| self._read_buf = b"" |
| return BufferedWriter.write(self, b) |
| |
| def flush(self): |
| BufferedWriter.flush(self) |
| |
| def close(self): |
| self.raw.close() |
| |
| |
| class TextIOBase(BufferedIOBase): |
| |
| """Base class for text I/O. |
| |
| This class provides a character and line based interface to stream I/O. |
| """ |
| |
| def read(self, n: int = -1) -> str: |
| """read(n: int = -1) -> str. Read at most n characters from stream. |
| |
| Read from underlying buffer until we have n characters or we hit EOF. |
| If n is negative or omitted, read until EOF. |
| """ |
| raise IOError(".read() not supported") |
| |
| def write(self, s: str): |
| """write(s: str) -> None. Write string s to stream. |
| """ |
| raise IOError(".write() not supported") |
| |
| def readline(self) -> str: |
| """readline() -> str. Read until newline or EOF. |
| |
| Returns an empty string if EOF is hit immediately. |
| """ |
| raise IOError(".readline() not supported") |
| |
| def __iter__(self): |
| """__iter__() -> Iterator. Return line iterator (actually just self). |
| """ |
| return self |
| |
| def next(self): |
| """Same as readline() except raises StopIteration on immediate EOF. |
| """ |
| line = self.readline() |
| if line == '': |
| raise StopIteration |
| return line |
| |
| # The following are provided for backwards compatibility |
| |
| def readlines(self, hint=None): |
| if hint is None: |
| return list(self) |
| n = 0 |
| lines = [] |
| while not lines or n < hint: |
| line = self.readline() |
| if not line: |
| break |
| lines.append(line) |
| n += len(line) |
| return lines |
| |
| def writelines(self, lines): |
| for line in lines: |
| self.write(line) |
| |
| |
| class TextIOWrapper(TextIOBase): |
| |
| """Buffered text stream. |
| |
| Character and line based layer over a BufferedIOBase object. |
| """ |
| |
| # XXX tell(), seek() |
| |
| def __init__(self, buffer, encoding=None, newline=None): |
| if newline not in (None, '\n', '\r\n'): |
| raise IOError("illegal newline %s" % newline) # XXX: ValueError? |
| if encoding is None: |
| # XXX This is questionable |
| encoding = sys.getfilesystemencoding() |
| if encoding is None: |
| encoding = "latin-1" # XXX, but this is best for transparancy |
| |
| self.buffer = buffer |
| self._encoding = encoding |
| self._newline = newline or os.linesep |
| self._fix_newlines = newline is None |
| self._decoder = None |
| self._pending = '' |
| |
| def fileno(self): |
| return self.buffer.fileno() |
| |
| def write(self, s: str): |
| return self.buffer.write(s.encode(self._encoding)) |
| |
| def _get_decoder(self): |
| make_decoder = codecs.getincrementaldecoder(self._encoding) |
| if make_decoder is None: |
| raise IOError(".readline() not supported for encoding %s" % |
| self._encoding) |
| decoder = self._decoder = make_decoder() # XXX: errors |
| if isinstance(decoder, codecs.BufferedIncrementalDecoder): |
| # XXX Hack: make the codec use bytes instead of strings |
| decoder.buffer = b"" |
| return decoder |
| |
| def read(self, n: int = -1): |
| decoder = self._decoder or self._get_decoder() |
| res = self._pending |
| if n < 0: |
| res += decoder.decode(self.buffer.read(), True) |
| self._pending = '' |
| return res |
| else: |
| while len(res) < n: |
| data = self.buffer.read(64) |
| res += decoder.decode(data, not data) |
| if not data: |
| break |
| self._pending = res[n:] |
| return res[:n] |
| |
| def readline(self): |
| line = self._pending |
| start = 0 |
| decoder = self._decoder or self._get_decoder() |
| |
| while True: |
| # In C we'd look for these in parallel of course. |
| nlpos = line.find("\n", start) |
| crpos = line.find("\r", start) |
| if nlpos >= 0 and crpos >= 0: |
| endpos = min(nlpos, crpos) |
| else: |
| endpos = nlpos if nlpos >= 0 else crpos |
| |
| if endpos != -1: |
| endc = line[endpos] |
| if endc == "\n": |
| ending = "\n" |
| break |
| |
| # We've seen \r - is it standalone, \r\n or \r at end of line? |
| if endpos + 1 < len(line): |
| if line[endpos+1] == '\n': |
| ending = "\r\n" |
| else: |
| ending = "\r" |
| break |
| # There might be a following \n in the next block of data ... |
| start = endpos |
| else: |
| start = len(line) |
| |
| # No line ending seen yet - get more data |
| while True: |
| data = self.buffer.read(64) |
| more_line = decoder.decode(data, not data) |
| if more_line != "" or not data: |
| break |
| |
| if more_line == "": |
| ending = '' |
| endpos = len(line) |
| break |
| |
| line += more_line |
| |
| nextpos = endpos + len(ending) |
| self._pending = line[nextpos:] |
| |
| # XXX Update self.newlines here if we want to support that |
| |
| if self._fix_newlines and ending != "\n" and ending != '': |
| return line[:endpos] + "\n" |
| else: |
| return line[:nextpos] |