lazy_wheel module

lazy_wheel is derived from pip’s wheel download code. It is really a seekable file-like based on HTTP range requests, backed by a sparse temporary file. Each read() issues one or more HTTP range requests to the URL depending on how much of the file has already been downloaded, while read()`s from already-fetched portions of the file are fulfilled by the backing file.

ZIP archives have a directory at the end of the file giving the offset to each compressed member. We fetch the directory, and then the portion of the file containing the member or members of interest, for a maximum of 3 requests to retrieve any individual file in the archive.

Lazy ZIP over HTTP

exception conda_package_streaming.lazy_wheel.HTTPRangeRequestUnsupported

Bases: Exception

class conda_package_streaming.lazy_wheel.LazyConda(url: str, session: Session, chunk_size: int = 10240)

Bases: LazyZipOverHTTP

prefetch(conda_file_id)

Conda fork specific. Prefetch the .info range from the remote archive. Reduces number of Range requests to 2 or 3 (1 or 2 for the directory, 1 for the file).

conda_file_id: name of .conda without path or .conda extension

class conda_package_streaming.lazy_wheel.LazyZipOverHTTP(url: str, session: Session, chunk_size: int = 10240)

Bases: object

File-like object mapped to a ZIP file over HTTP.

This uses HTTP range requests to lazily fetch the file’s content, which is supposed to be fed to ZipFile. If such requests are not supported by the server, raise HTTPRangeRequestUnsupported during initialization.

close() → None

Close the file.

property closed: bool

Whether the file is closed.

property mode: str

Opening mode, which is always rb.

property name: str

Path to the underlying file.

read(size: int = -1) → bytes

Read up to size bytes from the object and return them.

As a convenience, if size is unspecified or -1, all bytes until EOF are returned. Fewer than size bytes may be returned if EOF is reached.

readable() → bool

Return whether the file is readable, which is True.

seek(offset: int, whence: int = 0) → int

Change stream position and return the new absolute position.

Seek to offset relative position indicated by whence: * 0: Start of stream (the default). pos should be >= 0; * 1: Current position - pos may be negative; * 2: End of stream - pos usually negative.

seekable() → bool

Return whether random access is supported, which is True.

tell() → int

Return the current position.

truncate(size: int | None = None) → int

Resize the stream to the given size in bytes.

If size is unspecified resize to the current position. The current stream position isn’t changed.

Return the new file size.

writable() → bool

Return False.