The mutablestring module

The AbstractMutableString is the base of a parce Document.

It is a text string that is mutable via item and slice methods, the += operator and some methods like insert() and append().

If you make modifications while inside a context (using the Python context manager protocol), the modifications (that may not overlap then) are only applied when the context exits for the last time.

class AbstractMutableString(text='')

Bases: object

Abstract base class of a MutableString.

Defines the interface for interacting with the mutable string.

The only thing to implement is where the contents are actually stored, which is an implementation detail. To make a mutable string object work, you should at least implement:

• text() which should return the full text as a string.

• _update_text(changes) to update the text according to the changes. Those changes are a sorted iterable of (start, end, text) tuples, and will never overlap. All start/end positions refer to the original state of the text.

For efficiency reasons, you might want to reimplement:

• set_text() to replace all text in one go

• __len__() to get the length of the text

• _get_text() called by __getitem__ to get a slice or single character

text()

Should return the text contents.

set_text(text)

Set the text contents.

__str__()

Return the text contents.

__setitem__(key, text)

Replace the position or slice with text.

__delitem__(key)

Delete the chracter or slice of text.

__getitem__(key)

Get a character or a slice of text.

_update_text(changes)

Called to apply the changes to the text.

The changes is a sorted list of (start, end, text) tuples.

append(text)

Append text at the end of the document.

insert(pos, text)

Insert text at pos.

text_changed(position, removed, added)

Called after _update_text(). The default implementation does nothing.

class MutableString(text='')

Bases: AbstractMutableString

A Mutable string, storing the string contents in an internal attribute.

text()

Return the text.

_update_text(changes)

Apply the changes to the text.