Develop Reference

How to share and print class attributes with multi thread?

I have the program, which does stuff. And it counts how many times it has done some things by day and by hour. So I created a class and assigned it to hourly and daily.
And besides that, I have a multi thread function (let's call it background) which is used for the menu in the console. It is used to see/print or even modify variables. But it doesn't work. Every time I want it to print the class attributes, it always prints 0 for all attributes. How to fix this?
I also have this class and functions in separate modules
module a:
class Data():
def __init__(self,some_count):
self.some_count=some_count
daily=Data(0)
hourly=Data(0)
module b:
from a import daily,hourly
def print_data(command):
if command == "daily" :print(f"Daily saying hi is: {daily.some_count}")
if command == "hourly" :print(f"Hourly saying hi is: {hourly.some_count}")
background(): #It is used for menu. Depending on what you want, it can also print class attributes
while True:
print_data(input()) #you need to choose the command
module c:
from a import daily,hourly
from b import background
threading1 = threading.Thread(target=background) #
threading1.daemon = True #
threading1.start() #these 3 lines are copy pasted from my code
#this is the main function. And if you insert print(hourly.some_count) it will print the right value
while True:
hourly.some_count+=1
daily.some_count+=2
time.sleep(10000)
Note, this is not my code. Well it is, but just the idea. The above code is not functional, i just wanted to show, how i coded it.
I just don't know, why the function to print doesn't work. I assume that the "daily" and "hourly" class are mutated for a thread?
Perhaps it is a problem with imports? I have defined a class in module a, imported the "daily" and "hourly" in class b where I used in function. And then imported that function into module c where the main program is?
Thank you for help
EDIT, FOR THOSE WHO WANT AN ANSWER:
the solution below did not help.
I found a mistake myself later on and fixed it this way:
I made a seperate module, where i declared all the variables and classes. Only declaragion, no fuctions or any off that. And then i imported a varible or clas like this: From "class_declaration" import "name of class"
That way i can share the variable accros modules and threads

your concepts are correct: instance attributes changed in one thread should be visible in another thread. What I think might be wrong in your setup has to do with module naming and importing: some of the imports are ending internally as "myproject.a" and others just as "a": internally Python will create separate modules and separate objects.
If you uniformize the module names and containing directory in a Python package, everything should work as expected.
Try this: put all your .py modules in a folder containing an empty (0 bytes) file named __init__.py - and write your entry-point (the code from which your program will start running) in a file named __main__.py. Rewrite your imports to read from .a import daily, hourly (see the ".") -
and then from the parent of that directory, run the project with python -m <directory_name> - Python should execute the code in __main__.py and see all the other modules as part of the same package.

How to properly evaluate sage code from within a Python script

I've been trying to evaluate a simple "integrate(x,x)" statement from within Python, by following the Sage instructions for importing Sage into Python. Here's my entire script:
#!/usr/bin/env sage -python
from sage.all import *
def main():
integrate(x,x)
pass
main()
When I try to run it from the command line, I get this error thrown:
NameError: global name 'x' is not defined
I've tried adding var(x) into the script, global x, tried replacing integrate(x,x) with sage.integrate(x,x), but I can't seem to get it to work, I always get an error thrown.
The command I'm using is ./sage -python /Applications/path_to/script.py
I can't seem to understand what I'm doing wrong here.
Edit: I have a feeling it has something to do with the way I've "imported" sage. I have my a folder, let's call it folder 1, and inside of folder 1 is the "sage" folder and the "script.py"
I am thinking this because typing "sage." doesn't bring up any autocomplete options.

The name x is not imported by import sage.all. To define a variable x, you need to issue a var statement, like thus
var('x')
integrate(x,x)
or, better,
x = SR.var('x')
integrate(x,x)
the second example does not automagically inject the name x in the global scope, so that you have to explicitly assign it to a variable.

Here's what Sage does (see the file src/sage/all_cmdline.py):
from sage.all import *
from sage.calculus.predefined import x
If you put these lines in your Python file, then integrate(x,x) will work. (In fact, sage.calculus.predefined just defines x using the var function from sage.symbolic.ring; this just calls SR.var, as suggested in the other answer. But if you want to really imitate Sage's initialization process, these two lines are what you need.)

When is the name imported? And which namespace is it in? [duplicate]

I am learning Python and am still a beginner, although I have been studying it for about a year now. I am trying to write a module of functions which is called within a main module. Each of the functions in the called module needs the math module to run. I am wondering if there is a way to do this without importing the math module inside the called module. Here is what I have:
main.py:
from math import *
import module1
def wow():
print pi
wow()
module1.cool()
module1.py:
def cool():
print pi
When running main.py I get:
3.14159265359
Traceback (most recent call last):
File "Z:\Python\main.py", line 10, in <module>
module1.cool()
File "Z:\Python\module1.py", line 3, in cool
print pi
NameError: global name 'pi' is not defined
What I'm having a hard time understanding is why I get a name error when running main.py. I know that the variable pi becomes global to the main module upon import because wow can access it. I also know that cool becomes global to the main module upon import because I can print module1.cool and get <function cool at 0x02B11AF0>. So since cool is inside the global namespace of the main module, shouldn't the program first look inside the function cool for the variable pi, and then when it doesn't find it there, look inside main module for the variable pi and find it there?
The only way to get around this that I know of is to import the math module inside module1.py. I don't like the idea of that, though because it makes things more complicated and I am a fan of nice, simple code. I feel like I am close to grasping namespaces, but need help on this one. Thanks.

As the traceback shows, the problem isn't in main.py, but in module1.py:
Traceback (most recent call last):
File "Z:\Python\main.py", line 10, in <module>
module1.cool()
File "Z:\Python\module1.py", line 3, in cool
print pi
NameError: global name 'pi' is not defined
In other words, in module1, there is no global name pi, because you haven't imported it there. When you do from math import * in main.py, that just imports everything from the math module's namespace into the main module's namespace, not into every module's namespace.
I think the key thing you're missing here is that each module has its own "global" namespace. This can be a bit confusing at first, because in languages like C, there's a single global namespace shared by all extern variables and functions. But once you get past that assumption, the Python way makes perfect sense.
So, if you want to use pi from module1, you have to do the from math import * in module1.py. (Or you could find some other way to inject it—for example, module1.py could do from main import *, or main.py could do module1.pi = pi, etc. Or you could cram pi into the magic builtins/__builtin__ module, or use various other tricks. But the obvious solution is to do the import where you want it imported.)
As a side note, you usually don't want to do from foo import * anywhere except the interactive interpreter or, occasionally, the top-level script. There are exceptions (e.g., a few modules are explicitly designed to be used that way), but the rule of thumb is to either import foo or use a limited from foo import bar, baz.

"Explicit is better than implicit" is a design decision that was made by the creators of Python (launch python and run import this).
Therefore, when you run module1.cool(), Python will not look for the undefined pi in the main module.
You'll have to import the math module in explicitly whenever you want to use it - that's just how Python works.
Also, you should avoid from X import *-style imports, that's bad practice too. Here, you could do: from math import pi.

As others have said, there isn't actually a global pi in your module1. A good solution for you is this, which only imports pi once from math and explicitly ensures that the pi you're getting is the one from module1:
main.py:
import module1
def wow():
print module1.pi
wow()
module1.cool()
module1.py:
from math import pi
def cool():
print pi

The simple approach of exec (python 3) or execfile (python 2) as mentioned in the comments by #abarnert may be useful for some workflows. All that is needed is to replace the import line with:
exec( open("module1.py").read() ) # python 3
and then you can simply call the function with cool() rather than module1.cool(). Within cool(), the variable pi will behave like a global, as the OP had originally expected.
In a nutshell, this is simply hiding a function definition that would otherwise appear at the top of your main program and has both advantages and disadvantages. For large projects with multiple modules and imports, using exec (instead of a proper namespaces) is probably a mistake as you don't generally want to keep too many things within a single global namespace.
But for simple cases (like using Python as a shell script) exec gives you a simple and concise way to hide shared functions while letting them share the global namespace. Just note that in this case you might want to give extra thought to how you name your functions (e.g. use v1_cool and v2_cool to keep track of different versions since you can't do v1.cool and v2.cool).
One less obvious disadvantage of using exec here is that errors in the executed code may not display the line number of the error although you can work around this: how to get the line number of an error from exec or execfile in Python

Inside the module you could simply define from math import pi, which would only import pi from math but not the entire math module.

Pass variable between python scripts

I'm sure this is very simple but I've been unable to get it working correctly. I need to have my main python script call another python script and pass variables from the original script to the script that I've called
So for a simplistic example my first script is,
first.py
x = 5
import second
and my second script is,
second.py
print x
and I would expect it to print x but I get
NameError: name 'x' is not defined
I'm not sure if import is right way to achieve this, but if someone could shed light on it in a simple way that would be great!
thanks,
EDIT
After reading the comments I thought I would expand on my question. Aswin Murugesh answer fixes the import problem I was having, however the solution does not have the desired outcome as I can not seem to pass items in a list this way.
In first.py I have a list which I process as follows
for insert, (list) in enumerate(list, start =1):
'call second.py passing current list item'
I wanted to pass each item in the list to a second python file for further processing (web scraping), I didn't want to do this in first.py as this is meant to be the main 'scan' program which then calls other programs. I hope this now make more sense.
Thanks for the comments thus far.

When you call a script, the calling script can access the namespace of the called script. (In your case, first can access the namespace of second.) However, what you are asking for is the other way around. Your variable is defined in the calling script, and you want the called script to access the caller's namespace.
An answer is already stated in this SO post, in the question itself:
Access namespace of calling module
But I will just explain it here in your context.
To get what you want in your case, start off the called script with the following line:
from __main__ import *
This allows it to access the namespace (all variables and functions) of the caller script.
So now your calling script is, as before:
x=5
import second
and the called script is:
from __main__ import *
print x
This should work fine.

use the following script:
first.py:
x=5
second.py
import first
print first.x
this will print the x value. Always imported script data should be referenced with the script name, like in first.x

To avoid namespace pollution, import the variables you want individually: from __main__ import x, and so on. Otherwise you'll end up with naming conflicts you weren't aware of.

Try use exec
Python3.5:
first.py
x=5
exec(open('second.py').read())
second.py
print(x)
You can also pass x by using:
x=5
myVars = {'x':x}
exec(open('second.py').read(), myVars)
Not sure if this is a good way.

Finally,
I created a package for Python to solve this problem.
Install Guli from PIP.
$ pip install guli
Guli doesn't require installing any additional PIP package.
With the package you can
Guli can be used to pass between different Python scripts, between many processes or at the same script.
pass variables between main Process and another (Multiprocess) Process.
Pass variables between different Python scripts.
Pass variables between 'Main Process' and another (Multiprocess) Process.
Use variables at the same script.
Create / Delete / Edit - GuliVariables.
Example
import guli
import multiprocessing
string = guli.GuliVariable("hello").get()
print(string) # returns empty string ""
def my_function():
''' change the value from another process '''
guli.GuliVariable("hello").setValue(4)
multiprocessing.Process(target=my_function).start()
import time
time.sleep(0.01) # delay after process to catch the update
string = guli.GuliVariable("hello").get()
print(string) # returns "success!!!"
Hope I solved the problem for many people!

Namespaces with Module Imports

I am learning Python and am still a beginner, although I have been studying it for about a year now. I am trying to write a module of functions which is called within a main module. Each of the functions in the called module needs the math module to run. I am wondering if there is a way to do this without importing the math module inside the called module. Here is what I have:
main.py:
from math import *
import module1
def wow():
print pi
wow()
module1.cool()
module1.py:
def cool():
print pi
When running main.py I get:
3.14159265359
Traceback (most recent call last):
File "Z:\Python\main.py", line 10, in <module>
module1.cool()
File "Z:\Python\module1.py", line 3, in cool
print pi
NameError: global name 'pi' is not defined
What I'm having a hard time understanding is why I get a name error when running main.py. I know that the variable pi becomes global to the main module upon import because wow can access it. I also know that cool becomes global to the main module upon import because I can print module1.cool and get <function cool at 0x02B11AF0>. So since cool is inside the global namespace of the main module, shouldn't the program first look inside the function cool for the variable pi, and then when it doesn't find it there, look inside main module for the variable pi and find it there?
The only way to get around this that I know of is to import the math module inside module1.py. I don't like the idea of that, though because it makes things more complicated and I am a fan of nice, simple code. I feel like I am close to grasping namespaces, but need help on this one. Thanks.

As the traceback shows, the problem isn't in main.py, but in module1.py:
Traceback (most recent call last):
File "Z:\Python\main.py", line 10, in <module>
module1.cool()
File "Z:\Python\module1.py", line 3, in cool
print pi
NameError: global name 'pi' is not defined
In other words, in module1, there is no global name pi, because you haven't imported it there. When you do from math import * in main.py, that just imports everything from the math module's namespace into the main module's namespace, not into every module's namespace.
I think the key thing you're missing here is that each module has its own "global" namespace. This can be a bit confusing at first, because in languages like C, there's a single global namespace shared by all extern variables and functions. But once you get past that assumption, the Python way makes perfect sense.
So, if you want to use pi from module1, you have to do the from math import * in module1.py. (Or you could find some other way to inject it—for example, module1.py could do from main import *, or main.py could do module1.pi = pi, etc. Or you could cram pi into the magic builtins/__builtin__ module, or use various other tricks. But the obvious solution is to do the import where you want it imported.)
As a side note, you usually don't want to do from foo import * anywhere except the interactive interpreter or, occasionally, the top-level script. There are exceptions (e.g., a few modules are explicitly designed to be used that way), but the rule of thumb is to either import foo or use a limited from foo import bar, baz.

"Explicit is better than implicit" is a design decision that was made by the creators of Python (launch python and run import this).
Therefore, when you run module1.cool(), Python will not look for the undefined pi in the main module.
You'll have to import the math module in explicitly whenever you want to use it - that's just how Python works.
Also, you should avoid from X import *-style imports, that's bad practice too. Here, you could do: from math import pi.

As others have said, there isn't actually a global pi in your module1. A good solution for you is this, which only imports pi once from math and explicitly ensures that the pi you're getting is the one from module1:
main.py:
import module1
def wow():
print module1.pi
wow()
module1.cool()
module1.py:
from math import pi
def cool():
print pi

The simple approach of exec (python 3) or execfile (python 2) as mentioned in the comments by #abarnert may be useful for some workflows. All that is needed is to replace the import line with:
exec( open("module1.py").read() ) # python 3
and then you can simply call the function with cool() rather than module1.cool(). Within cool(), the variable pi will behave like a global, as the OP had originally expected.
In a nutshell, this is simply hiding a function definition that would otherwise appear at the top of your main program and has both advantages and disadvantages. For large projects with multiple modules and imports, using exec (instead of a proper namespaces) is probably a mistake as you don't generally want to keep too many things within a single global namespace.
But for simple cases (like using Python as a shell script) exec gives you a simple and concise way to hide shared functions while letting them share the global namespace. Just note that in this case you might want to give extra thought to how you name your functions (e.g. use v1_cool and v2_cool to keep track of different versions since you can't do v1.cool and v2.cool).
One less obvious disadvantage of using exec here is that errors in the executed code may not display the line number of the error although you can work around this: how to get the line number of an error from exec or execfile in Python

Inside the module you could simply define from math import pi, which would only import pi from math but not the entire math module.