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Diffstat (limited to 'Lib/StringIO.py')
| -rw-r--r-- | Lib/StringIO.py | 324 |
1 files changed, 0 insertions, 324 deletions
diff --git a/Lib/StringIO.py b/Lib/StringIO.py deleted file mode 100644 index 815bce6..0000000 --- a/Lib/StringIO.py +++ /dev/null @@ -1,324 +0,0 @@ -r"""File-like objects that read from or write to a string buffer. - -This implements (nearly) all stdio methods. - -f = StringIO() # ready for writing -f = StringIO(buf) # ready for reading -f.close() # explicitly release resources held -flag = f.isatty() # always false -pos = f.tell() # get current position -f.seek(pos) # set current position -f.seek(pos, mode) # mode 0: absolute; 1: relative; 2: relative to EOF -buf = f.read() # read until EOF -buf = f.read(n) # read up to n bytes -buf = f.readline() # read until end of line ('\n') or EOF -list = f.readlines()# list of f.readline() results until EOF -f.truncate([size]) # truncate file at to at most size (default: current pos) -f.write(buf) # write at current position -f.writelines(list) # for line in list: f.write(line) -f.getvalue() # return whole file's contents as a string - -Notes: -- Using a real file is often faster (but less convenient). -- There's also a much faster implementation in C, called cStringIO, but - it's not subclassable. -- fileno() is left unimplemented so that code which uses it triggers - an exception early. -- Seeking far beyond EOF and then writing will insert real null - bytes that occupy space in the buffer. -- There's a simple test set (see end of this file). -""" -try: - from errno import EINVAL -except ImportError: - EINVAL = 22 - -__all__ = ["StringIO"] - -def _complain_ifclosed(closed): - if closed: - raise ValueError, "I/O operation on closed file" - -class StringIO: - """class StringIO([buffer]) - - When a StringIO object is created, it can be initialized to an existing - string by passing the string to the constructor. If no string is given, - the StringIO will start empty. - - The StringIO object can accept either Unicode or 8-bit strings, but - mixing the two may take some care. If both are used, 8-bit strings that - cannot be interpreted as 7-bit ASCII (that use the 8th bit) will cause - a UnicodeError to be raised when getvalue() is called. - """ - def __init__(self, buf = ''): - # Force self.buf to be a string or unicode - if not isinstance(buf, basestring): - buf = str(buf) - self.buf = buf - self.len = len(buf) - self.buflist = [] - self.pos = 0 - self.closed = False - - def __iter__(self): - return self - - def __next__(self): - """A file object is its own iterator, for example iter(f) returns f - (unless f is closed). When a file is used as an iterator, typically - in a for loop (for example, for line in f: print line), the __next__() - method is called repeatedly. This method returns the next input line, - or raises StopIteration when EOF is hit. - """ - _complain_ifclosed(self.closed) - r = self.readline() - if not r: - raise StopIteration - return r - - def close(self): - """Free the memory buffer. - """ - if not self.closed: - self.closed = True - del self.buf, self.pos - - def isatty(self): - """Returns False because StringIO objects are not connected to a - tty-like device. - """ - _complain_ifclosed(self.closed) - return False - - def seek(self, pos, mode = 0): - """Set the file's current position. - - The mode argument is optional and defaults to 0 (absolute file - positioning); other values are 1 (seek relative to the current - position) and 2 (seek relative to the file's end). - - There is no return value. - """ - _complain_ifclosed(self.closed) - if self.buflist: - self.buf += ''.join(self.buflist) - self.buflist = [] - if mode == 1: - pos += self.pos - elif mode == 2: - pos += self.len - self.pos = max(0, pos) - - def tell(self): - """Return the file's current position.""" - _complain_ifclosed(self.closed) - return self.pos - - def read(self, n=None): - """Read at most size bytes from the file - (less if the read hits EOF before obtaining size bytes). - - If the size argument is negative or omitted, read all data until EOF - is reached. The bytes are returned as a string object. An empty - string is returned when EOF is encountered immediately. - """ - _complain_ifclosed(self.closed) - if self.buflist: - self.buf += ''.join(self.buflist) - self.buflist = [] - if n is None: - n = -1 - if n < 0: - newpos = self.len - else: - newpos = min(self.pos+n, self.len) - r = self.buf[self.pos:newpos] - self.pos = newpos - return r - - def readline(self, length=None): - r"""Read one entire line from the file. - - A trailing newline character is kept in the string (but may be absent - when a file ends with an incomplete line). If the size argument is - present and non-negative, it is a maximum byte count (including the - trailing newline) and an incomplete line may be returned. - - An empty string is returned only when EOF is encountered immediately. - - Note: Unlike stdio's fgets(), the returned string contains null - characters ('\0') if they occurred in the input. - """ - _complain_ifclosed(self.closed) - if self.buflist: - self.buf += ''.join(self.buflist) - self.buflist = [] - i = self.buf.find('\n', self.pos) - if i < 0: - newpos = self.len - else: - newpos = i+1 - if length is not None: - if self.pos + length < newpos: - newpos = self.pos + length - r = self.buf[self.pos:newpos] - self.pos = newpos - return r - - def readlines(self, sizehint = 0): - """Read until EOF using readline() and return a list containing the - lines thus read. - - If the optional sizehint argument is present, instead of reading up - to EOF, whole lines totalling approximately sizehint bytes (or more - to accommodate a final whole line). - """ - total = 0 - lines = [] - line = self.readline() - while line: - lines.append(line) - total += len(line) - if 0 < sizehint <= total: - break - line = self.readline() - return lines - - def truncate(self, size=None): - """Truncate the file's size. - - If the optional size argument is present, the file is truncated to - (at most) that size. The size defaults to the current position. - The current file position is not changed unless the position - is beyond the new file size. - - If the specified size exceeds the file's current size, the - file remains unchanged. - """ - _complain_ifclosed(self.closed) - if size is None: - size = self.pos - elif size < 0: - raise IOError(EINVAL, "Negative size not allowed") - elif size < self.pos: - self.pos = size - self.buf = self.getvalue()[:size] - self.len = size - - def write(self, s): - """Write a string to the file. - - There is no return value. - """ - _complain_ifclosed(self.closed) - if not s: return - # Force s to be a string or unicode - if not isinstance(s, basestring): - s = str(s) - spos = self.pos - slen = self.len - if spos == slen: - self.buflist.append(s) - self.len = self.pos = spos + len(s) - return - if spos > slen: - self.buflist.append('\0'*(spos - slen)) - slen = spos - newpos = spos + len(s) - if spos < slen: - if self.buflist: - self.buf += ''.join(self.buflist) - self.buflist = [self.buf[:spos], s, self.buf[newpos:]] - self.buf = '' - if newpos > slen: - slen = newpos - else: - self.buflist.append(s) - slen = newpos - self.len = slen - self.pos = newpos - - def writelines(self, iterable): - """Write a sequence of strings to the file. The sequence can be any - iterable object producing strings, typically a list of strings. There - is no return value. - - (The name is intended to match readlines(); writelines() does not add - line separators.) - """ - write = self.write - for line in iterable: - write(line) - - def flush(self): - """Flush the internal buffer - """ - _complain_ifclosed(self.closed) - - def getvalue(self): - """ - Retrieve the entire contents of the "file" at any time before - the StringIO object's close() method is called. - - The StringIO object can accept either Unicode or 8-bit strings, - but mixing the two may take some care. If both are used, 8-bit - strings that cannot be interpreted as 7-bit ASCII (that use the - 8th bit) will cause a UnicodeError to be raised when getvalue() - is called. - """ - if self.buflist: - self.buf += ''.join(self.buflist) - self.buflist = [] - return self.buf - - -# A little test suite - -def test(): - import sys - if sys.argv[1:]: - file = sys.argv[1] - else: - file = '/etc/passwd' - lines = open(file, 'r').readlines() - text = open(file, 'r').read() - f = StringIO() - for line in lines[:-2]: - f.write(line) - f.writelines(lines[-2:]) - if f.getvalue() != text: - raise RuntimeError, 'write failed' - length = f.tell() - print('File length =', length) - f.seek(len(lines[0])) - f.write(lines[1]) - f.seek(0) - print('First line =', repr(f.readline())) - print('Position =', f.tell()) - line = f.readline() - print('Second line =', repr(line)) - f.seek(-len(line), 1) - line2 = f.read(len(line)) - if line != line2: - raise RuntimeError, 'bad result after seek back' - f.seek(len(line2), 1) - list = f.readlines() - line = list[-1] - f.seek(f.tell() - len(line)) - line2 = f.read() - if line != line2: - raise RuntimeError, 'bad result after seek back from EOF' - print('Read', len(list), 'more lines') - print('File length =', f.tell()) - if f.tell() != length: - raise RuntimeError, 'bad length' - f.truncate(length/2) - f.seek(0, 2) - print('Truncated length =', f.tell()) - if f.tell() != length/2: - raise RuntimeError, 'truncate did not adjust length' - f.close() - -if __name__ == '__main__': - test() |