Develop Reference

What is the best way to allow user to configure a Python package

I have situation like this. I am creating a Python package. That Python package needs to use Redis, so I want to allow the user of the package to define the Redis url.
Here's how I attempted to do it:
bin/main.py
from my_package.main import run
from my_package.config import config
basicConfig(filename='logs.log', level=DEBUG)
# the user defines the redis url
config['redis_url'] = 'redis://localhost:6379/0'
run()
my_package/config.py
config = {
"redis_url": None
}
my_package/main.py
from .config import config
def run():
print(config["redis_url"]) # prints None instead of what I want
Unfortunately, it doesn't work. In main.py the value of config["redis_url"] is None instead of the url defined in bin/main.py file. Why is that? How can I make it work?
I could pass the config to the run() function, but then if I run some other function I will need to pass the config to that function as well. I'd like to pass it one time ideally.

Passing parameters to a cli using exec in python

I have the following situation.
I have a cli made in python in another folder and I have a function that receives some parameters and needs to be passed to the cli through an exec.
Estrutura de pastas
-execs
-fil1e.py
main.py
I tried to do it that way and it didn't work:
My main file
import sys
n = sys.argv [0]
stream = open ("execs / file1.py", n)
read_file = stream.read ()
exec(read_file)

Why are environment variables empty in Flask apps?

I have a flask app (my_app) that calls a function in a different file (my_function):
my_app.py:
from my_functions import my_function
#app.route('/')
def index():
my_function()
return render_template('index.html')
my_functions.py:
def my_function():
try:
import my_lib
except:
print("my_lib not found in system!")
# do stuff...
if __name__ == "__main__":
my_function()
When I execute my_functions.py directly (i.e., python my_functions.py) "my_lib" is imported without error; however, when I execute the flask app (i.e., python my_app.py) I get an import error for "my_lib".
When I print the LD_LIBRARY_PATH variable at the beginning of each file:
print(os.environ['LD_LIBRARY_PATH'])
I get the correct value when calling my_functions.py, but get no value (empty) when calling my_app.py.Trying to set this value at the beginning of my_app.py has no effect:
os.environ['LD_LIBRARY_PATH'] = '/usr/local/lib'
Questions:
(1) Why is 'LD_LIBRARY_PATH' empty when called within the Flask app?
(2) How do I set it?
Any help appreciated.

LD_LIBRARY_PATH is cleared when executing the flask app, likely for security reasons as Mike suggested.
To get around this, I use subprocess to make a call directly to an executable:
import subprocess
call_str = "executable_name -arg1 arg1_value -arg2 arg2_value"
subprocess.call(call_str, shell=True, stderr=subprocess.STDOUT)
Ideally the program should be able to use the python bindings, but for now calling the executable works.

WLST execute stored variable "connect()" statement

So, I am passing a environment variable from bash to python;
#!/usr/bin/env python2
import os
#connect("weblogic", "weblogic", url=xxx.xxx.xxx.xxx:xxxx)
os.environ['bash_variable']
via wlst.sh I can print exported bash_variable, but how do I execute stored variable? Basically, I am trying to remove the original connect statement and pass a variable that has said information. Thanks

Question though, why wouldn't you called the script with the variable as an argument and use sys.argv[] ?
By example something like this.
import os
import sys
import traceback
from java.io import *
from java.lang import *
wlDomain = sys.argv[1]
wlDomPath = sys.argv[2]
wlNMHost = sys.argv[3]
wlNMPort = sys.argv[4]
wlDPath="%s/%s" %(wlDomPath,wlDomain)
wlNMprop="/apps/bea/wls/scripts/.shadow/NM.prop"
try:
print "Connection to Node Manager"
print ""
loadProperties(wlNMprop)
nmConnect(username=NMuser,password=NMpass,host=wlNMHost,port=wlNMPort,domainName=wlDomain,domainDir=wlDPath,mType='ssl',verbose='true')
except:
print "Fatal Error : No Connection to Node Manager"
exit()
print "Connected to Node Manager"
The NM.prop file is a 600 file with the username/password for the NM.
EDIT :
So from what I understand you want to do something like this :
URLS = ['t3s://Host1:Port1','t3s://Host2:Port2','t3s://Host3:Port3']
for urls in URLS:
connect('somebody','password',urls)
{bunch of commands}
disconnect()
And the values of the list URLS would be define by the environment.
The way I see it you have 3 choices :
Have 1 script per environment, more or less identical save for the URLS list
Have 1 script but with a conditionnal branching on sys.argv[1] (the environment as a parameter) and create the list there.
Have 1 script which use a parameter file for each environment according to the environment. Each parameter file containing the list in question.
Something like that :
propENV = sys.argv[1]
propPath = "/path1/path2"
propFile = "%s/%s" %(propPath,propENV)
loadProperties(propFile)
I would probably use the properties file option myself as it is more flexible from an operational standpoint...at least IMHO.

Passing own arguments to ryu proxy app

I am developing ryu app. The app is basically a python script. The ryu apps are invoked by ryu-manager like this
ryu-manager {filename}
There are certain parameters that are taken by ryu-manager. I want to know if there is a way i could pass arguments to my file?
argparse module of python to parse command line options is there but am not sure it will work as all arguments I provide are used by ryu-manager not my script.
Any help would be appreciated.

I haven't tried this, but:
"Ryu currently uses oslo.config.cfg for command-line parsing.
(ryu/contrib/oslo/config).
There are several examples in the tree. ryu/app/tunnel_port_updater.py"
from
http://comments.gmane.org/gmane.network.ryu.devel/2709
see also
https://github.com/osrg/ryu/blob/master/ryu/app/tunnel_port_updater.py
The Ryu 'getting started' page simply suggests:
ryu-manager [--flagfile <path to configuration file>] [generic/application specific options…]
http://www.osrg.net/ryu/_sources/getting_started.txt

Doing so is a 4-step process. I'll show an example where you read parameters and then print them, but you could assign them to variables or do whatever you would like to by referencing this process.
Create a .conf file (e.g. params.conf)
#Example Conf File
[DEFAULT]
param1_int = 42
param2_str = "You read my data :)"
param3_list = 1,2,3
param4_float = 3.14
Add the following code to your __init__ method. I did this to the simple_switch_13.py which comes with ryu:
from ryu import cfg
:
:
class SimpleSwitch13(app_manager.RyuApp):
def __init__(self, *args, **kwargs):
super(SimpleSwitch13, self).__init__(*args, **kwargs)
:
CONF = cfg.CONF
CONF.register_opts([
cfg.IntOpt('param1_int', default=0, help = ('The ultimate answer')),
cfg.StrOpt('param2_str', default='default', help = ('A string')),
cfg.ListOpt('param3_list', default = None, help = ('A list of numbers')),
cfg.FloatOpt('param4_float', default = 0.0, help = ('Pi? Yummy.'))])
print 'param1_int = {}'.format(CONF.param1_int))
print 'param2_str = {}'.format(CONF.param2_str))
print 'param3_list = {}'.format(CONF.param3_list))
print 'param4_float = {}'.format(CONF.param4_float))
Run Script
ryu-manager paramtest.py --config-file [PATH/TO/FILE/params.conf]
Profit
I referenced the following when putting together my answer, they can provide more detail (such as the oslo.config stuff, which I had never heard of prior to running into this issue).
More info on oslo.config: http://www.giantflyingsaucer.com/blog/?p=4822
Ryu email chain on this issue: https://sourceforge.net/p/ryu/mailman/message/33410077/

I have not found a way to pass arguments to a ryu controller. One way that I have used to get around this is to pass arguments as an environment variable. For example, I have a program which invokes ryu-manager and needs to pass a parameter to the app. I do this as follows: ARG=value ryu-manager app.py