# \_io

File-like objects that read from or write to a string buffer.

This implements (nearly) all stdio methods.

```python
f = StringIO()      # ready for writing
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 ('') 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)
```

**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).

## \_io.StringIO(buf='')

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.


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