optools/ref/python.tips_tricks_and_dirty_hacks

This is a collection of snippets that I tend to use frequently, or would need
in the future.

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To programmatically import a list of modules by name:
_____
import importlib

mods = ['os', 'sys', 'shutil', 'platform']

for m in mods:
    globals()[m] = importlib.import_module(m)
_____
you can then use them as if you did:

import os
import sys
import shutil
import platform
etc.

this breaks pep-8, but sometimes you need to programmatically import modules.

ref: https://www.python.org/dev/peps/pep-0008/#imports

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To programmatically install modules via pip if they aren't installed:

____
import importlib
import pip

# I don't  *think* pip/pypi is case-sensitive, but frequently module names are
# not the same as their package names. ugh.
# The key is the package name, the value is the module name. We use the above
# trick here to try to import and install if it fails.
mods = {'PyMySQL': 'pymysql',
        'Jinja2': 'jinja2',
        'psutil': None,  # We show off a little bit here with this, see below.
        'paramiko': None}  # ""

for m in mods.keys():
    modname = mods[m]
    if not modname:
        modname = m
    try:
        globals()[modname] = importlib.import_module(modname)
    except ImportError:
        # We use --user to avoid conflicts with the host's python system.
        # pip.main() accepts all of pip (commandline)'s args!
        pip.main(['install', '--user', m])
        try:
            globals()[modname] = importlib.import_module(modname)
        except ImportError:
            raise RuntimeError('Unable to install {0}!'.format(m))
____

###############################################################################

To convert an argparse set of parsed arguments into a dict from a class, you
simply do:
____
def GenArgs():
    args = argparse.ArgumentParser()
    # args here
    return(args)

def somefunc():
    args = vars(GenArgs().parse_args())
____
"args" in somefunc is a dict now.

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To dynamically allocate class parameters into constants from a dict (such as
from argparse - see above), do something like this:
____
class ClassName(object):
    def __init__(self, **kwargs):
        for i in kwargs.keys():
            setattr(self, i, kwargs[i])
----

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To store stdout and stderr to different files in a subprocess call:
----
with open('/tmp/test.o', 'w') as out, open('/tmp/test.e', 'w') as err:
    subprocess.run(['command'], stdout = out, stderr = err)
----
###############################################################################

To use optools logging lib (or other "shared" modules):
----
import os
import re
import importlib
spec = importlib.util.spec_from_file_location(
                                       'logger',
                                       '/opt/dev/optools/lib/python/logger.py')
logger = importlib.util.module_from_spec(spec)
spec.loader.exec_module(logger)
log = logger.log(name = 'project.name')
----

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# TODO #
https://stackoverflow.com/questions/10265193/python-can-a-class-act-like-a-module