Hi,
There are 4 main ways to run Python:
(1) python -m module [...]
(2) python script.py [...]
(3) python -c code [...]
(4) python [...]
(1) and (2) insert the directory of the module/script at sys.path[0].
(3) and (4) insert an empty string at sys.path[0].
This behavior is convenient and is maybe part of Python usability
success: importing a module in the current directory is as easy as
"import other_module" (load other_module.py). But it's also a threat
to security: an attacker can override a stdlib module by creating a
Python script with the same name than a stdlib module, like os.py or
shutil.py.
People learning Python commonly create a file with the same name than
a stdlib module (ex: random.py) and then are clueless in face of an
ImportError exception.
Changing the default behavior was discussed multiple times. No
consensus was reached, maybe because most users like the current
default behavior and are not affected by corner cases (see below).
I propose adding a -P option to Python command line interface to "not
add sys.path[0]":
https://github.com/python/cpython/pull/31542
See the documentation in the PR for the exact behavior of this option.
I prefer to add an environment variable, only pass the option
explicitly on the command line.
Since Python 3.4, there is already the -I ("isolated mode") option:
https://docs.python.org/dev/using/cmdline.html#cmdoption-I
The -I option has other effects like disabling user site directories,
it option doesn't fit use cases of the -P option.
One annoying issue of the Python default behavior is that running a
script in /usr/bin/ as root can create or override .pyc files in the
/usr directory, even in the /usr/bin/ directory. Example of this
surprising and annoying issue:
https://github.com/benjaminp/six/issues/359#issuecomment-996159668
The -P option can be used in #!/usr/bin/python shebang to avoid this issue.
--
An alternative would be to change the default behavior to not add
sys.path[0], and add an option to opt-in for Python 3.10 behavior.
Here are my notes about it:
https://github.com/vstinner/misc/blob/main/cpython/pep_path0.rst
What do you think?
Victor
--
Night gathers, and now my watch begins. It shall not end until my death.
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There are 4 main ways to run Python:
(1) python -m module [...]
(2) python script.py [...]
(3) python -c code [...]
(4) python [...]
(1) and (2) insert the directory of the module/script at sys.path[0].
(3) and (4) insert an empty string at sys.path[0].
This behavior is convenient and is maybe part of Python usability
success: importing a module in the current directory is as easy as
"import other_module" (load other_module.py). But it's also a threat
to security: an attacker can override a stdlib module by creating a
Python script with the same name than a stdlib module, like os.py or
shutil.py.
People learning Python commonly create a file with the same name than
a stdlib module (ex: random.py) and then are clueless in face of an
ImportError exception.
Changing the default behavior was discussed multiple times. No
consensus was reached, maybe because most users like the current
default behavior and are not affected by corner cases (see below).
I propose adding a -P option to Python command line interface to "not
add sys.path[0]":
https://github.com/python/cpython/pull/31542
See the documentation in the PR for the exact behavior of this option.
I prefer to add an environment variable, only pass the option
explicitly on the command line.
Since Python 3.4, there is already the -I ("isolated mode") option:
https://docs.python.org/dev/using/cmdline.html#cmdoption-I
The -I option has other effects like disabling user site directories,
it option doesn't fit use cases of the -P option.
One annoying issue of the Python default behavior is that running a
script in /usr/bin/ as root can create or override .pyc files in the
/usr directory, even in the /usr/bin/ directory. Example of this
surprising and annoying issue:
https://github.com/benjaminp/six/issues/359#issuecomment-996159668
The -P option can be used in #!/usr/bin/python shebang to avoid this issue.
--
An alternative would be to change the default behavior to not add
sys.path[0], and add an option to opt-in for Python 3.10 behavior.
Here are my notes about it:
https://github.com/vstinner/misc/blob/main/cpython/pep_path0.rst
What do you think?
Victor
--
Night gathers, and now my watch begins. It shall not end until my death.
_______________________________________________
Python-Dev mailing list -- python-dev@python.org
To unsubscribe send an email to python-dev-leave@python.org
https://mail.python.org/mailman3/lists/python-dev.python.org/
Message archived at https://mail.python.org/archives/list/python-dev@python.org/message/IU5Q2AXAURFVDPRWNU3BDFVKV2QX5NOR/
Code of Conduct: http://python.org/psf/codeofconduct/