lazysequence
A lazy sequence makes an iterator look like an immutable sequence:
from lazysequence import lazysequence
def load_records():
return range(10) # let's pretend this is expensive
records = lazysequence(load_records())
if not records:
raise SystemExit("no records found")
first, second = records[:2]
print("The first record is", first)
print("The second record is", second)
for record in records.release(): # do not cache all records in memory
print("record", record)Why?
Sometimes you need to peek ahead at items returned by an iterator. But what if later code needs to see all the items from the iterator? Then you have some options:
Pass any consumed items separately. This can get messy, though.
Copy the iterator into a sequence beforehand, if that does not take a lot of space or time.
Duplicate the iterator using itertools.tee, or write your own custom itertool that buffers consumed items internally. There are some good examples of this approach on SO, by Alex Martelli, Raymond Hettinger, and Ned Batchelder.
A lazy sequence combines advantages from option 2 and option 3. It is an immutable sequence that wraps the iterable and caches consumed items in an internal buffer. By implementing collections.abc.Sequence, lazy sequences provide the full set of sequence operations on the iterable. Unlike a copy (option 2), but like a duplicate (option 3), items are only consumed and stored in memory as far as required for any given operation.
There are some caveats:
The lazy sequence will eventually store all items in memory. If this is a problem, use s.release() to obtain an iterator over the sequence items without further caching. After calling this function, the sequence should no longer be used.
Explicit is better than implicit. Clients may be better off being passed an iterator and dealing with its limitations. For example, clients may not expect len(s) to incur the cost of consuming the iterator to its end.
Installation
You can install lazysequence via pip from PyPI:
$ pip install lazysequenceContributing
Contributions are very welcome. To learn more, see the Contributor Guide.
License
Distributed under the terms of the MIT license, lazysequence is free and open source software.
Issues
If you encounter any problems, please file an issue along with a detailed description.
Credits
This project was generated from @cjolowicz’s Hypermodern Python Cookiecutter template.
1 maintainer
Metadata
1 maintainer
Release files for lazysequence 0.3.0
For a detailed explanation of source distributions (sdists) and built distributions (wheels), please see the package formats documentation.
Source distribution (sdist)
| File | Size | Uploaded | Provenance | |
|---|---|---|---|---|
| lazysequence-0.3.0.tar.gz | 7.6 kB | Without provenance | Details |
Built distribution (wheel)
| File | Interpreter | ABI | Platform | Reset |
|---|---|---|---|---|
| lazysequence-0.3.0-py3-none-any.whl | Python 3 | none | any | Details |
Total release size: 14.8 kB
Release files / lazysequence-0.3.0.tar.gz
| Download URL | lazysequence-0.3.0.tar.gz |
|---|---|
| Size | 7.6 kB |
| Tags | Source |
|
SHA-256 checksum How to use checksums |
f5712a80f3bb14d2d77ccb777aad7d327fe9d4dc4cba0393247780d83d2b2fe0
|
|
BLAKE2b-256 checksum How to use checksums |
e29728728ae0e2c0ec4a2cb8d7030a2e8f2356b4d246b461cfe4993a91e1f85f
|
| Upload date | |
|
Uploaded using Trusted Publishing? What is trusted publishing? |
No |
| Uploaded via |
twine/3.4.1 importlib_metadata/4.6.1 pkginfo/1.7.1 requests/2.26.0 requests-toolbelt/0.9.1 tqdm/4.61.2 CPython/3.9.6
|
Release files / lazysequence-0.3.0-py3-none-any.whl
| Download URL | lazysequence-0.3.0-py3-none-any.whl |
|---|---|
| Size | 7.1 kB |
| Tags | Python 3 |
|
SHA-256 checksum How to use checksums |
8f01e3499d17dae6020947ea15df3c3c2b7fa66f7d2a6f1548aed5e050bba927
|
|
BLAKE2b-256 checksum How to use checksums |
dd95bd5e24669aa21c6238861410ba3b4743e1e9486680de4e7c630e37bbd886
|
| Upload date | |
|
Uploaded using Trusted Publishing? What is trusted publishing? |
No |
| Uploaded via |
twine/3.4.1 importlib_metadata/4.6.1 pkginfo/1.7.1 requests/2.26.0 requests-toolbelt/0.9.1 tqdm/4.61.2 CPython/3.9.6
|
Security for lazysequence 0.3.0
Provenance
Provenance describes where a file came from. On PyPI, provenance is shared via attestations, which provide a verifiable record of the build or publishing details. View details, limitations and caveats.
No provenance found
None of the files in this release were uploaded with provenance metadata.
A note on package security
PyPI is a repository for distributing packages, not a service for auditing them. While third-party security researchers and our staff do their best to detect and remove malicious packages, PyPI cannot guarantee the quality, security or suitability of any given package.
To learn more about protecting yourself from malicious actors, visit our package security documentation.
