ImportError: No module named pexpect

Question

I am using Fabric and would like to use fexpect. I have the following Python script:

from ilogue.fexpect import expect, expecting, run

(...)

def install_postgresql(profile):
print("!!! Installing PostgreSQL...")
print(' -> Doing pre-cleanup...')

# Remove PostgreSQL if it exists

prompts = []
prompts += expect('Do you want to continue [Y/n]? ', 'Y')

with settings(warn_only=True):
    with expecting(prompts):
        run('sudo apt-get purge postgresql')

print(' -> Doing actual installation...')

# Install PostgreSQL

prompts = []
prompts += expect('Do you want to continue [Y/n]? ', 'Y')

with expecting(prompts):
    run('sudo apt-get install postgresql')

# In some cases PostgreSQL has issues with Ubuntu's default kernel params
# that prevent PostgreSQL to start automatically, so we try to start it
# TODO: Fix it
with settings(warn_only=True):
    run('sudo service postgresql start')

When executing I get the following error:

[xxx.xxx.xxx.xxx] out: Traceback (most recent call last):
[xxx.xxx.xxx.xxx] out:   File "/tmp/fexpect_MbW3QP6Zpy5KBjBGQcaYxi", line 4, in <module>
[xxx.xxx.xxx.xxx] out:     import pexpect
[xxx.xxx.xxx.xxx] out: ImportError: No module named pexpect

I am using virtualenv and pexpect is actually installed:

(venv)PALM00545424A:woopup i841712$ pip install pexpect
Requirement already satisfied (use --upgrade to upgrade): pexpect in ./venv/lib/python2.7/site-packages

Answer 1

Found the solution.

pexpect was not part of the remote machine's Python installation.

I simply executed

sudo -E pip install pexpect 

on the remote machine.

Answer 2

In fact if your script uses fexcept, the command you need to run is actually:

sudo -E pip install fexpect 

Answer 3

Not a direct answer to your question, but tools like chef, puppet or salt are more suitable for installing system packages.

Answer 4

I got the same error when using pexpect lib to interact with gatttool. I used Pycharm to remote debug code on Raspberry pi. Here is the command processed by Pycharm and the error output

sudo+ssh://pi3@192.168.x.x:22/usr/bin/python3 -u /tmp/pycharm_project_55/Rasp_Pi/BluetoothBLEComm.py
Traceback (most recent call last):
  File "/tmp/pycharm_project_55/Rasp_Pi/BluetoothBLEComm.py", line 33, in <module>
    import pexpect
ModuleNotFoundError: No module named 'pexpect'

After spending few hours, I identified the issue is with the option I checked while configuring the Remote Python Interpreter in Pycharm. It is the option that executes code with root privileges via sudo.

**sudo**+ssh://pi3@192.168.x.x:22/usr/bin/python3...

The pexpect package was only installed for my local pi3 user. So to solve the issue either I had to install pexpect using sudo or uncheck the option that executes the code with root privileges.