I need to extend a shell script (Bash). As I am much more familiar with Python I want to do this by writing some lines of Python code which depends on variables from the shell script. Adding an extra python file is not an option.
result=`python -c "import stuff; print('all $code in one very long line')"`
is not very readable.
I would prefer to specify my Python code as a multiline string and then execute it.
Use a here-doc:
result=$(python <<EOF
import stuff
print('all $code in one very long line')
EOF
)
<<EOF allows injection attacks -- <<'EOF' and requiring variables to be passed in via command line or environment is much safer.Thanks to this Stack Overflow answer, I found the answer myself:
#!/bin/bash
# Some Bash code
END_VALUE=10
PYTHON_CODE=$(cat <<END
# Python code starts here
import math
for i in range($END_VALUE):
print(i, math.sqrt(i))
# Python code ends here
END
)
# Use the
res="$(python3 -c "$PYTHON_CODE")"
# Continue with Bash code
echo "$res"
a, b = "foo", "bar" are imho not possible in bash.
stdinYou can avoid the need for here-doc. In Bash and Z shell (executable zsh), you can use single quotes as in:
export PYTORCH_ENABLE_MPS_FALLBACK=1
python3 -c '
from transformers import pipeline
import torch
device = "mps" if torch.backends.mps.is_available() else "cpu"
pipe = pipeline("sentiment-analysis", device=device)
result = pipe("Nobody expects the Spanish inquisition!")
print(result)
'
❗ make sure to avoid single quotes in the actual python code
$code that needs to be replaced. Variables don't get replaced inside single quotes.
python python3 -c ' print('\"$code\"') ' (line ends are chomped in comments)python -c "print('$code')". It would be best if you showed it in the answer.python3 -m this says that readability counts ;)shell: python (available in all ootb runners) and do everything in python, including accessing env vars, but that's a different story..You can simply use a here-document:
result=$(python <<EOF
import stuff
code = "${code}"
print("Hello from Python")
print("Code variable is:", code)
EOF
)
This way the Python code stays readable, and Bash variables like $code are expanded correctly
$code is a security bug, not a feature. You don't want a shell variable containing " + os.system("rm -rf ~") + " to run rm. There are safe ways to transport shell variables into embedded Python scripts, but this isn't one of them.