bpo-21417: Add compresslevel= to the zipfile module (GH-5385)

This allows the compression level to be specified when writing zipfiles
(for the entire file *and* overridden on a per-file basis).

Contributed by Bo Bayles

1 files changed, 32 insertions, 12 deletions

diff --git a/Doc/library/zipfile.rst b/Doc/library/zipfile.rst
index 5b8c776..d58efe0 100644
--- a/Doc/library/zipfile.rst
+++ b/Doc/library/zipfile.rst
@@ -130,10 +130,12 @@ ZipFile Objects
 ---------------
 
 
-.. class:: ZipFile(file, mode='r', compression=ZIP_STORED, allowZip64=True)
+.. class:: ZipFile(file, mode='r', compression=ZIP_STORED, allowZip64=True, \
+                   compresslevel=None)
 
    Open a ZIP file, where *file* can be a path to a file (a string), a
    file-like object or a :term:`path-like object`.
+
    The *mode* parameter should be ``'r'`` to read an existing
    file, ``'w'`` to truncate and write a new file, ``'a'`` to append to an
    existing file, or ``'x'`` to exclusively create and write a new file.
@@ -145,16 +147,27 @@ ZipFile Objects
    adding a ZIP archive to another file (such as :file:`python.exe`).  If
    *mode* is ``'a'`` and the file does not exist at all, it is created.
    If *mode* is ``'r'`` or ``'a'``, the file should be seekable.
+
    *compression* is the ZIP compression method to use when writing the archive,
    and should be :const:`ZIP_STORED`, :const:`ZIP_DEFLATED`,
    :const:`ZIP_BZIP2` or :const:`ZIP_LZMA`; unrecognized
-   values will cause :exc:`NotImplementedError` to be raised.  If :const:`ZIP_DEFLATED`,
-   :const:`ZIP_BZIP2` or :const:`ZIP_LZMA` is specified but the corresponding module
-   (:mod:`zlib`, :mod:`bz2` or :mod:`lzma`) is not available, :exc:`RuntimeError`
-   is raised. The default is :const:`ZIP_STORED`.  If *allowZip64* is
-   ``True`` (the default) zipfile will create ZIP files that use the ZIP64
-   extensions when the zipfile is larger than 4 GiB. If it is  false :mod:`zipfile`
-   will raise an exception when the ZIP file would require ZIP64 extensions.
+   values will cause :exc:`NotImplementedError` to be raised.  If
+   :const:`ZIP_DEFLATED`, :const:`ZIP_BZIP2` or :const:`ZIP_LZMA` is specified
+   but the corresponding module (:mod:`zlib`, :mod:`bz2` or :mod:`lzma`) is not
+   available, :exc:`RuntimeError` is raised. The default is :const:`ZIP_STORED`.
+
+   If *allowZip64* is ``True`` (the default) zipfile will create ZIP files that
+   use the ZIP64 extensions when the zipfile is larger than 4 GiB. If it is
+   ``false`` :mod:`zipfile` will raise an exception when the ZIP file would
+   require ZIP64 extensions.
+
+   The *compresslevel* parameter controls the compression level to use when
+   writing files to the archive.
+   When using :const:`ZIP_STORED` or :const:`ZIP_LZMA` it has no effect.
+   When using :const:`ZIP_DEFLATED` integers ``0`` through ``9`` are accepted
+   (see :class:`zlib <zlib.compressobj>` for more information).
+   When using :const:`ZIP_BZIP2` integers ``1`` through ``9`` are accepted
+   (see :class:`bz2 <bz2.BZ2File>` for more information).
 
    If the file is created with mode ``'w'``, ``'x'`` or ``'a'`` and then
    :meth:`closed <close>` without adding any files to the archive, the appropriate
@@ -187,6 +200,9 @@ ZipFile Objects
    .. versionchanged:: 3.6.2
       The *file* parameter accepts a :term:`path-like object`.
 
+   .. versionchanged:: 3.7
+      Add the *compresslevel* parameter.
+
 
 .. method:: ZipFile.close()
 
@@ -351,13 +367,15 @@ ZipFile Objects
       :exc:`ValueError`.  Previously, a :exc:`RuntimeError` was raised.
 
 
-.. method:: ZipFile.write(filename, arcname=None, compress_type=None)
+.. method:: ZipFile.write(filename, arcname=None, compress_type=None, \
+                          compresslevel=None)
 
    Write the file named *filename* to the archive, giving it the archive name
    *arcname* (by default, this will be the same as *filename*, but without a drive
    letter and with leading path separators removed).  If given, *compress_type*
    overrides the value given for the *compression* parameter to the constructor for
-   the new entry.
+   the new entry. Similarly, *compresslevel* will override the constructor if
+   given.
    The archive must be open with mode ``'w'``, ``'x'`` or ``'a'``.
 
    .. note::
@@ -383,7 +401,8 @@ ZipFile Objects
       a :exc:`RuntimeError` was raised.
 
 
-.. method:: ZipFile.writestr(zinfo_or_arcname, data[, compress_type])
+.. method:: ZipFile.writestr(zinfo_or_arcname, data, compress_type=None, \
+                             compresslevel=None)
 
    Write the string *data* to the archive; *zinfo_or_arcname* is either the file
    name it will be given in the archive, or a :class:`ZipInfo` instance.  If it's
@@ -393,7 +412,8 @@ ZipFile Objects
 
    If given, *compress_type* overrides the value given for the *compression*
    parameter to the constructor for the new entry, or in the *zinfo_or_arcname*
-   (if that is a :class:`ZipInfo` instance).
+   (if that is a :class:`ZipInfo` instance). Similarly, *compresslevel* will
+   override the constructor if given.
 
    .. note::