(uv internal error) Failed to spawn the python child process.: The system cannot find the file specified.

[konosubakonoakua]

imp_blm_test on  main [!?⇡] via 🐍 v3.11.9 (imp_blm_test)                                                                                                       
❯ uv venv --seed -p 3.11 -n .venv                                                                                                                                

imp_blm_test on  main [!?⇡] via 🐍 v3.11.9 (imp_blm_test) 
❯ . .\.venv\Scripts\activate.ps1

imp_blm_test on  main [!?⇡] via 🐍 v3.11.9 (imp_blm_test) took 9s
❯ uv --version
uv 0.2.35 (e097f948c 2024-08-09)

imp_blm_test on  main [!?⇡] via 🐍 v3.11.9 (imp_blm_test) 
❯ pip
Received error code: 2
(uv internal error) Failed to spawn the python child process.: The system cannot find the file specified.

imp_blm_test on  main [!?⇡] via 🐍 v3.11.9 (imp_blm_test) 
❯ uv run ipython --preview
warning: `uv run` is experimental and may change without warning
Received error code: 2
(uv internal error) Failed to spawn the python child process.: The system cannot find the file specified.

imp_blm_test on  main [!?⇡] via 🐍 v3.11.9 (imp_blm_test) 
❯ uv pip
Manage Python packages with a pip-compatible interface

Usage: uv.exe pip [OPTIONS] <COMMAND>

Related to #1779 #1988

[charliermarsh]

Unfortunately I have no idea what's happening here.

[FishAlchemist]

I have been unable to duplicate this issue on my Windows 11 x86-64.
It works fine without any errors.

Only uv run ipython --preview has this error

ipython: error: argument --preview: expected one argument

[zanieb]

Note: You can't pass the --preview flag to ipython.

uv internal error is coming from the trampoline

uv/crates/uv-trampoline/src/bounce.rs

Line 472 in 2cd63f0

"(uv internal error) {}: {}.{}",

and the error is from

uv/crates/uv-trampoline/src/bounce.rs

Lines 299 to 318 in 2cd63f0

	let mut child_process_info = PROCESS_INFORMATION::default();
	unsafe {
	CreateProcessA(
	None,
	// Why does this have to be mutable? Who knows. But it's not a mistake --
	// MS explicitly documents that this buffer might be mutated by CreateProcess.
	PSTR::from_raw(child_cmdline.as_ptr() as *mut _),
	None,
	None,
	true,
	PROCESS_CREATION_FLAGS(0),
	None,
	None,
	si,
	&mut child_process_info,
	)
	}
	.unwrap_or_else(|_| {
	print_last_error_and_exit("Failed to spawn the python child process");
	});

cc @konstin and @samypr100

[samypr100]

Interesting, I just tried the above example (with seed) and was unable to replicate on Windows 10 x86-64 both with 0.2.33 and 0.2.35. What does your pyvenv.cfg look like?

uv run ipython --preview
warning: `uv run` is experimental and may change without warning
usage: ipython [-h] [--debug] [--show-config] [--show-config-json] [--quiet] [--init] [--autoindent] [--no-autoindent] [--automagic] [--no-automagic] [--pdb] [--no-pdb] [--pprint] [--no-pprint] [--color-info] [--no-color-info] [--ignore-cwd] [--no-ignore-cwd] [--nosep] [--autoedit-syntax]
               [--no-autoedit-syntax] [--simple-prompt] [--no-simple-prompt] [--banner] [--no-banner] [--confirm-exit] [--no-confirm-exit] [--term-title] [--no-term-title] [--classic] [--quick] [-i] [--log-level TerminalIPythonApp.log_level] [--profile-dir ProfileDir.location]
               [--profile TerminalIPythonApp.profile] [--ipython-dir TerminalIPythonApp.ipython_dir] [--config TerminalIPythonApp.extra_config_file] [--autocall TerminalInteractiveShell.autocall] [--colors TerminalInteractiveShell.colors] [--logfile TerminalInteractiveShell.logfile]
               [--logappend TerminalInteractiveShell.logappend] [-c TerminalIPythonApp.code_to_run] [-m TerminalIPythonApp.module_to_run] [--ext TerminalIPythonApp.extra_extensions] [--gui TerminalIPythonApp.gui] [--pylab [TerminalIPythonApp.pylab]] [--matplotlib [TerminalIPythonApp.matplotlib]]
               [--cache-size TerminalInteractiveShell.cache_size]
               [extra_args ...]
ipython: error: argument --preview: expected one argument

[konosubakonoakua]

@samypr100
here it is.

imp_blm_test\.venv on  main [!?⇡] via 🐍 v3.11.9 (imp_blm_test) 
❯ cat .\pyvenv.cfg           
home = C:\Users\me\AppData\Local\Programs\Python\Python311
implementation = CPython
uv = 0.2.24
version_info = 3.11.9
include-system-site-packages = false
prompt = imp_blm_test

and here's python I have installed.

imp_blm_test\.venv on  main [!?⇡] via 🐍 v3.11.9 (imp_blm_test) 
❯ uv python list
warning: `uv python list` is experimental and may change without warning
cpython-3.12.4-windows-x86_64-none     C:\Users\me\AppData\Local\Programs\Python\Python312\python.exe
cpython-3.12.4-windows-x86_64-none     <download available>
cpython-3.11.9-windows-x86_64-none     C:\Users\me\AppData\Local\Programs\Python\Python311\python.exe
cpython-3.11.9-windows-x86_64-none     C:\Users\me\AppData\Roaming\uv\data\python\cpython-3.11.9-windows-x86_64-none\python.exe
cpython-3.10.14-windows-x86_64-none    <download available>
cpython-3.9.19-windows-x86_64-none     <download available>
cpython-3.8.19-windows-x86_64-none     C:\Users\me\AppData\Roaming\uv\data\python\cpython-3.8.19-windows-x86_64-none\python.exe
pypy-3.7.13-windows-x86_64-none        C:\Users\me\AppData\Roaming\uv\data\python\pypy-3.7.13-windows-x86_64-none\python.exe

[joelvaneenwyk]

I ran into a similar issue with same/similar error of "(uv internal error) Failed to spawn the python child process..." and discovered that it was caused by inadvertently naming my project script "python" in my pyproject.toml e.g.,

[project.scripts]
python = "my_project.main"

If you add this package as a dependency, it generates a python.exe that overwrites the "real" one, causing all sorts of chaos. Renaming the script (for example, mytool = "my_project.main") fixed the problem.

Not sure what the best solution here is. Clearly user error in my case but an error/warning (did I miss one?) would be worthwhile or maybe not allow 'uv sync' to overwrite managed executables like 'python'?

[samypr100]

@joelvaneenwyk Can you open a separate issue with your finding?

I ran into a similar issue with same/similar error of "(uv internal error) Failed to spawn the python child process..." and discovered that it was caused by inadvertently naming my project script "python" in my pyproject.toml e.g.,

[project.scripts]
python = "my_project.main"
If you add this package as a dependency, it generates a python.exe that overwrites the "real" one, causing all sorts of chaos. Renaming the script (for example, mytool = "my_project.main") fixed the problem.

Not sure what the best solution here is. Clearly user error in my case but an error/warning (did I miss one?) would be worthwhile or maybe not allow 'uv sync' to overwrite managed executables like 'python'?

Arguably we should probably not be generating scripts that clobber the ones needed to run scripts, but I do see the same issue with pip 😆. In linux this manifests a bit differently with the error being instead something like too many levels of symbolic links.