Table of Contents
It depends on unrar command-line utility to do the actual decompression.
Note that by default it expect it to be in PATH. If unrar launching fails, you need to fix this.
No, rarfile parses RAR structure in Python code. Also it can read uncompressed files from archive without external utility.
No. The current architecture - parsing in Python and decompression with command line tools work well across all interesting operating systems (Windows/Linux/MacOS), wrapping a library does not bring any advantages.
Simple execution of command-line tools is also legally simpler situation than linking with external library.
On Windows the unrar.exe is not in PATH so simple Popen("unrar ..") does not work. It can be solved several ways:
Include rarfile.py and/or unrar with your application.
No. RARLAB is not interested in RAR becoming open format and specifically discourages writing RAR creation software.
In the meantime use either Zip (better compatibility) or 7z (better compression) format for your own archives.
RarFile uses unrar to extract compressed files. But when extracting single file from archive containing many entries, unrar needs to parse whole archive until it finds the right entry. This makes random-access to entries slow. To avoid that, RarFile remembers location of compressed data for each entry and on read it copies it to temporary archive containing only data for that one file, thus making unrar fast.
The logic is only activated for entries smaller than HACK_SIZE_LIMIT (20M by default). Bigger files are accessed directly from RAR.
Note - it only works for non-solid archives. So if you care about random access to files in your archive, do not create solid archives.