I'm getting "No such file or directory: 'psql'" when I try to run a psql command with Python subprocess. What am I doing wrong?

I’m using a psql command to try and list all the databases in a local postgres instance.
Here’s the command I’m trying to run:

psql --host localhost --port 55000 --username postgres -At --command 'SELECT datname FROM pg_database WHERE NOT datistemplate AND datallowconn ORDER BY datname;' postgres

But when I try using subprocess in a python script to execute the command, I’m running into a problem:

FileNotFoundError: [Errno 2] No such file or directory: 'psql'

Here’s my code:

import subprocess
import shlex

source_host = "localhost"
source_port = "55000"
source_user = "postgres"
source_password = "postgrespw"
database_select_query = "SELECT datname FROM pg_database WHERE NOT datistemplate AND datallowconn ORDER BY datname;"

database_select_command = f"""
    psql \
        --host {source_host} \
        --port {source_port} \
        --username {source_user} \
        -At --command '{database_select_query}' \
    postgres
"""
print(database_select_command)
print(shlex.split(database_select_command))
output = subprocess.run(
    shlex.split(database_select_command),
    capture_output=True,
    shell=False,
    env={"PGPASSWORD": source_password},
)
print(output)

The weird thing is the command works perfectly fine if I try it on my command line outside of python subprocess. I’ve tried escaping the quotes, I’ve tried putting it all one one line, but to no avail.

What am I missing here?

>Solution :

psql is likely not in your python’s PATH. Call it by its absolute path instead:

database_select_command = f"""
    /usr/bin/psql \
        --host {source_host} \
        --port {source_port} \
        --username {source_user} \
        -At --command '{database_select_query}' \
    postgres
"""

If you’re unsure what the path is, run which psql to find out.