10.5 The StringIO and cStringIO Modules
You can implement file-like objects by
writing Python classes that supply the methods you need. If all you
want is for data to reside in memory rather than on a file as seen by
the operating system, you can use the StringIO or
cStringIO module. The two modules are almost
identical: each supplies a factory function to create in-memory
file-like objects. The difference between them is that objects
created by module StringIO are instances of class
StringIO.StringIO. You may inherit from this class
to create your own customized file-like objects, overriding the
methods that you need to specialize. Objects created by module
cStringIO, on the other hand, are instances of a
special-purpose type, not of a class. Performance is much better when
you can use cStringIO, but inheritance is not
feasible. Furthermore, cStringIO does not support
Unicode.
Each module supplies a factory function named
StringIO that creates a file-like object
fl.
Creates and returns an in-memory file-like object
fl, with all methods and attributes of a
built-in file object. The data contents of
fl are initialized to be a copy of
argument str, which must be a plain string
for the StringIO factory function in
cStringIO, while it can be a plain or Unicode
string for the function in StringIO.
Besides all methods and attributes of built-in file objects, as
covered in Section 10.3.2 earlier in
this chapter, fl supplies one
supplementary method, getvalue.
Returns the current data contents of fl as
a string. You cannot call
fl.getvalue after you
call fl.close:
close frees the buffer that
fl internally keeps, and
getvalue needs to access the buffer to yield its
result.
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