https://github.com/python/cpython/commit/35d8ac7cd7ed6cd3d84af721dce970da59bd5f68
commit: 35d8ac7cd7ed6cd3d84af721dce970da59bd5f68
branch: main
author: Cody Maloney <[email protected]>
committer: hauntsaninja <[email protected]>
date: 2024-08-16T13:52:41-07:00
summary:
GH-120754: Disable buffering in Path.read_bytes (#122111)
`Path.read_bytes()` is used to read a whole file. buffering /
BufferedIO is focused around making small, possibly interleaved,
read/write efficient which doesn't add value in this case.
On my Mac, running the benchmark:
```python
import pyperf
from pathlib import Path
def read_all(all_paths):
for p in all_paths:
p.read_bytes()
def read_file(path_obj):
path_obj.read_bytes()
all_rst = list(Path("Doc").glob("**/*.rst"))
all_py = list(Path(".").glob("**/*.py"))
assert all_rst, "Should have found rst files"
assert all_py, "Should have found python source files"
runner = pyperf.Runner()
runner.bench_func("read_file_small", read_file, Path("Doc/howto/clinic.rst"))
runner.bench_func("read_file_large", read_file, Path("Doc/c-api/typeobj.rst"))
```
before:
```python
.....................
read_file_small: Mean +- std dev: 6.80 us +- 0.07 us
.....................
read_file_large: Mean +- std dev: 10.8 us +- 0.2 us
````
after:
```python
.....................
read_file_small: Mean +- std dev: 5.67 us +- 0.05 us
.....................
read_file_large: Mean +- std dev: 9.77 us +- 0.52 us
```
files:
A Misc/NEWS.d/next/Library/2024-07-22-08-57-28.gh-issue-120754.Eo5puP.rst
M Lib/pathlib/_abc.py
M Lib/test/test_pathlib/test_pathlib_abc.py
diff --git a/Lib/pathlib/_abc.py b/Lib/pathlib/_abc.py
index 500846d19cf811..720756cac66f68 100644
--- a/Lib/pathlib/_abc.py
+++ b/Lib/pathlib/_abc.py
@@ -585,7 +585,7 @@ def read_bytes(self):
"""
Open the file in bytes mode, read it, and close the file.
"""
- with self.open(mode='rb') as f:
+ with self.open(mode='rb', buffering=0) as f:
return f.read()
def read_text(self, encoding=None, errors=None, newline=None):
diff --git a/Lib/test/test_pathlib/test_pathlib_abc.py
b/Lib/test/test_pathlib/test_pathlib_abc.py
index 629a1d4bdeb4de..f222fd5b1ec082 100644
--- a/Lib/test/test_pathlib/test_pathlib_abc.py
+++ b/Lib/test/test_pathlib/test_pathlib_abc.py
@@ -1464,7 +1464,7 @@ def stat(self, *, follow_symlinks=True):
def open(self, mode='r', buffering=-1, encoding=None,
errors=None, newline=None):
- if buffering != -1:
+ if buffering != -1 and not (buffering == 0 and 'b' in mode):
raise NotImplementedError
path_obj = self.resolve()
path = str(path_obj)
diff --git
a/Misc/NEWS.d/next/Library/2024-07-22-08-57-28.gh-issue-120754.Eo5puP.rst
b/Misc/NEWS.d/next/Library/2024-07-22-08-57-28.gh-issue-120754.Eo5puP.rst
new file mode 100644
index 00000000000000..daf184153646cd
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2024-07-22-08-57-28.gh-issue-120754.Eo5puP.rst
@@ -0,0 +1 @@
+``Pathlib.read_bytes`` no longer opens the file in Python's buffered I/O mode.
This reduces overheads as the code reads a file in whole leading to a modest
speedup.
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