[Question] __file__ is not defined

[anzhi0708]

So my SConstruct looks like this

import re
import os
from pathlib import Path


source_files_path_prefix = Path(__file__).parent / 'src'
source_files = [source_files_path_prefix / filename for filename in os.listdir(source_files_path_prefix)]

print(source_files)

If I run this text file via Python 3.13, it will print

me@MyMacBook-Air ~/d/hello-scons> python SConstruct
[PosixPath('/Users/me/Projects/experimental/hello-scons/src/main.cpp')]

but if I run scons command, it will print

scons: Reading SConscript files ...
NameError: name '__file__' is not defined:
  File "/Users/me/Projects/experimental/hello-scons/SConstruct", line 6:
    source_files_path_prefix = Path(__file__).parent / 'src'

I thought SConstruct files are regular python scripts?

[mwichmann]

Strictly speaking, they're not standalone Python scripts - if they were, you'd have to be importing all of the things that form the SCons API. Instead, they are snippets (potentially very large ones) written in Python that are evaluated (actually, compiled then exec'd) in the context of SCons. While the result you get surprises me (not defined), you won't get what you are looking for here: the context while the SConstruct/SConscript is being run is actually .../SCons/Script/SConscript.py.

If you're looking for a way to generate a list of files in a particular directory, SCons provides some ways that might help - see, in particular:

https://scons.org/doc/production/HTML/scons-man.html#f-Glob

To SCons' file-handling routines, # is a synonym for top directory of the build (which is equivalent to asking pathlib for "parent of SConstruct"), though be aware that won't work for any pure-Python code, only for SCons calls. So try:

source_files = Glob('#/src')   # returns a list of nodes
# or
source_files = Glob('#/src', strings=True)  # returns a list of strings

Glob has the advantage of finding files that don't exist now, but might (that is, files generated by SCons during the run).

[anzhi0708]

Very cool approach, thanks for explaining!