This module implements a file-like class, StringIO, that reads and writes a string buffer (also known as memory files). See the description of file objects for operations (section File Objects). (For standard strings, see str and unicode.)
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. In both cases, the initial file position starts at zero.
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.
The following methods of StringIO objects require special mention:
import StringIO output = StringIO.StringIO() output.write('First line.\n') print >>output, 'Second line.' # Retrieve file contents -- this will be # 'First line.\nSecond line.\n' contents = output.getvalue() # Close object and discard memory buffer -- # .getvalue() will now raise an exception. output.close()
The module cStringIO provides an interface similar to that of the StringIO module. Heavy use of StringIO.StringIO objects can be made more efficient by using the function StringIO() from this module instead.
Since this module provides a factory function which returns objects of built-in types, there’s no way to build your own version using subclassing. Use the original StringIO module in that case.
Unlike the memory files implemented by the StringIO module, those provided by this module are not able to accept Unicode strings that cannot be encoded as plain ASCII strings.
Calling StringIO() with a Unicode string parameter populates the object with the buffer representation of the Unicode string, instead of encoding the string.
Another difference from the StringIO module is that calling StringIO() with a string parameter creates a read-only object. Unlike an object created without a string parameter, it does not have write methods. These objects are not generally visible. They turn up in tracebacks as StringI and StringO.
The following data objects are provided as well:
There is a C API to the module as well; refer to the module source for more information.
import cStringIO output = cStringIO.StringIO() output.write('First line.\n') print >>output, 'Second line.' # Retrieve file contents -- this will be # 'First line.\nSecond line.\n' contents = output.getvalue() # Close object and discard memory buffer -- # .getvalue() will now raise an exception. output.close()