Package nltk :: Module util :: Class AbstractLazySequence

Class AbstractLazySequence

object --+
         |
        AbstractLazySequence

Known Subclasses:

An abstract base class for read-only sequences whose values are computed as needed. Lazy sequences act like tuples -- they can be indexed, sliced, and iterated over; but they may not be modified.

The most common application of lazy sequences in NLTK is for corpus view objects, which provide access to the contents of a corpus without loading the entire corpus into memory, by loading pieces of the corpus from disk as needed.

The result of modifying a mutable element of a lazy sequence is undefined. In particular, the modifications made to the element may or may not persist, depending on whether and when the lazy sequence caches that element's value or reconstructs it from scratch.

Subclasses are required to define two methods:

Instance Methods

[hide private]

__len__(self)
Return the number of tokens in the corpus file underlying this corpus view.

source code

iterate_from(self, start)
Return an iterator that generates the tokens in the corpus file underlying this corpus view, starting at the token number start. source code

__getitem__(self, i)
Return the ith token in the corpus file underlying this corpus view. source code

__iter__(self)
Return an iterator that generates the tokens in the corpus file underlying this corpus view.

source code

count(self, value)
Return the number of times this list contains value. source code

index(self, value, start=None, stop=None)
Return the index of the first occurance of value in this list that is greater than or equal to start and less than stop. source code

__contains__(self, value)
Return true if this list contains value. source code

__add__(self, other)
Return a list concatenating self with other.

source code

__radd__(self, other)
Return a list concatenating other with self.

source code

__mul__(self, count)
Return a list concatenating self with itself count times. source code

__rmul__(self, count)
Return a list concatenating self with itself count times. source code

__repr__(self)
Returns: A string representation for this corpus view that is similar to a list's representation; but if it would be more than 60 characters long, it is truncated.

source code

__cmp__(self, other)
Return a number indicating how self relates to other. source code

__hash__(self)
hash(x)

source code

Inherited from object: __delattr__, __getattribute__, __init__, __new__, __reduce__, __reduce_ex__, __setattr__, __str__

Class Variables

[hide private]

_MAX_REPR_SIZE = 60

Properties

[hide private]

Inherited from object: __class__

Method Details

[hide private]

iterate_from(self, start)

source code

Return an iterator that generates the tokens in the corpus file underlying this corpus view, starting at the token number start. If start>=len(self), then this iterator will generate no tokens.

getitem(self, i)
(Indexing operator)

source code

Return the ith token in the corpus file underlying this corpus view. Negative indices and spans are both supported.

index(self, value, start=None, stop=None)

source code

Return the index of the first occurance of value in this list that is greater than or equal to start and less than stop. Negative start & stop values are treated like negative slice bounds -- i.e., they count from the end of the list.

repr(self)
(Representation operator)

source code

repr(x)

Returns:: A string representation for this corpus view that is similar to a list's representation; but if it would be more than 60 characters long, it is truncated.
Overrides: object.__repr__

cmp(self, other)
(Comparison operator)

source code

Return a number indicating how self relates to other.

If other is not a corpus view or a list, return -1.
Otherwise, return cmp(list(self), list(other)).

Note: corpus views do not compare equal to tuples containing equal elements. Otherwise, transitivity would be violated, since tuples do not compare equal to lists.

hash(self)
(Hashing function)

source code

hash(x)

Raises:

ValueError - Corpus view objects are unhashable.

Overrides: object.__hash__

Class AbstractLazySequence

iterate_from(self, start)

__getitem__(self, i) (Indexing operator)

index(self, value, start=None, stop=None)

__repr__(self) (Representation operator)

__cmp__(self, other) (Comparison operator)

__hash__(self) (Hashing function)

getitem(self, i)
(Indexing operator)

repr(self)
(Representation operator)

cmp(self, other)
(Comparison operator)

hash(self)
(Hashing function)