I am trying to get a python script to open another python script in a directory that I know of but the actual filename is a variable. I would like to execute this file or be able to import the file (either way would work for what I am trying to do) but I am having problems with each one.
for trying to execute it, the dos style box appears but quickly disappears, too quickyl to really do anything. I even added a Raw_Input() and executed the file on its own and got it to work. here is the like on code:
os.system("python actions/"+Script)
Script being the name of the python file in a string. I know that the file is found but the problem is that it disapears too quickly
the other way I am trying to do it is by importing the file:
import 'actions/'+Script
this is the only logical way I can think of to import the damn thing but I keep getting syntax errors
Use the __import__ function to import a module whose name isn't known until runtime:
# Import the module
mymodule = __import__('actions/' + Script)
# Call functions in the module etc.
mymodule.do_something(42);
Or try import (been around a while I believe) or importlib (added in python 2.7):
import">http://docs.python.org/library/functions.html#import
http://docs.python.org/library/importlib.html#importlib.import_module
try:
import sys
sys.path = ["./actions"] + sys.path
exec("import " + Script[-3])
Related
How to run another python scripts in a different folder?
I have main program:
calculation_control.py
In the folder calculation_folder, there is calculation.py
How do I run calculation_folder/calculation.py from within calculation_control.py?
So far I have tried the following code:
calculation_file = folder_path + "calculation.py"
if not os.path.isfile(parser_file) :
continue
subprocess.Popen([sys.executable, parser_file])
There are more than a few ways. I'll list them in order of inverted
preference (i.e., best first, worst last):
Treat it like a module: import file. This is good because it's secure, fast, and maintainable. Code gets reused as it's supposed
to be done. Most Python libraries run using multiple methods stretched
over lots of files. Highly recommended. Note that if your file is
called file.py, your import should not include the .py
extension at the end.
The infamous (and unsafe) exec command: execfile('file.py'). Insecure, hacky, usually the wrong answer.
Avoid where possible.
Spawn a shell process: os.system('python file.py'). Use when desperate.
Source: How can I make one python file run another?
Solution
Python only searches the current directory for the file(s) to import. However, you can work around this by adding the following code snippet to calculation_control.py...
import sys
sys.path.insert(0, 'calculation_folder') # Note: if this relavtive path doesn't work or produces errors try replacing it with an absolute path
import calculation
This question already has an answer here:
Why Python print my output two times when I import the same file in which I am printing?
(1 answer)
Closed 2 years ago.
Here is the code
import random
print("Hello", end="")
print("twice")
and a screenshot of the code
When I execute this code it for some reason is running twice. The problem seems to be from the import random statement, because if I either remove that statement or import some other module it works fine.
What could be the reason for this, should I reinstall Python on my system.
There's nothing wrong with python.
The reason is simple:
Your module is importing itself (because it is also named random) - this has to do with the lookup mechanics of python. python will try to import from your root folder first, before modules from pythonpath are imported.
From the docs:
When a module named spam is imported, the interpreter first searches for a built-in module with that name. If not found, it then searches for a file named spam.py in a list of directories given by the variable sys.path. sys.path is initialized from these locations:
The directory containing the input script (or the current directory
when no file is specified).
PYTHONPATH (a list of directory names, with the same syntax as the shell variable PATH).
The installation-dependent default.
Since your file (module) is called random.py, import random will import this very file.
Now, what does "import" mean?
The statement import something will cause Python to lookup the name something, starting with the current directory.
Therefore, import random will result in an import of this very file, since its name will shadow the build-in random.
Besides, if the name to import is already in the namespace, then the import statement is ignored.
Once the module to import has been located, its code is executed.
As a result, the flow of your script is as follow:
Lookup the random.py name
Add random to the namespace
Execute the code contained in random.py
The random name already exists in the namespace, so the import random statement is ignored
Print the text
Print the text
The reason for this is you've named the script random.py and inside it you import random.
random will not import the built-in random module but, rather, the random module you've created. This leads to the script executing the same statements twice (and also leads to other ugly errors if you tried and import something from random, like from random import randrange.)
Renaming the script leads to normal behavior.
Because your scripts is called random.py, so when you import random you are executing your script as well. Mind to name correctly your scripts.
your python script is named random.py so when you import random it import itself , in python when you import module it will run it.
therefor you get print twice.
rename your script or remove the import
I am currently trying to debug an app that I have not written myself. I have narrowed the problem down to a particular method that is imported from a module outside of the current script. I would like to step through this module by writing to a file at each step, however it doesn't seem to work.
I have a version of the app that is running correctly and when I write to a file from within the module, the script runs fine but no file is created. Am I missing something here?
Example
Script that I am debugging
from module import method
example code ...
method(data) --- where error occurs
more code ...
module.py
def method(data):
file = open('filetowrite.txt','w')
file.write('something ....')
file.close()
Do not reinvent the wheel, use standard logging module.
Since you mentioned "I would like to step through this module" that's how you can do it with again standard pdb module.
Your code for file writing looks fine. I would look at the path (the location) where the file is being written to.
Check out:
How to get full path of current file's directory in Python?
I understand how to actually link python files, however, i don't understand how to get variable's from these linked files. I've tried to grab them and I keep getting NameError.
How do I go about doing this? The reason i want to link files is to simply neaten up my script and not make it 10000000000 lines long. Also, in the imported python script, do i have to import everything again? Another question, do i use the self function when using another scripts functions?
ie;
Main Script:
import sys, os
import importedpyfile
Imported Py File
import sys, os
I understand how to actually link python files, however, i don't
understand how to get variable's from these linked files. I've tried
to grab them and I keep getting NameError.
How are you doing that? Post more code. For instance, the following works:
file1.py
#!/usr/bin/env python
from file2 import file2_func, file2_variable
file2_func()
print file2_variable
file2.py:
#!/usr/bin/env python
file2_variable = "I'm a variable!"
def file2_func():
print "Hello World!"
Also, in the imported python script, do i have to import everything
again?
Nope, modules should be imported when the python interpreter reads that file.
Another question, do i use the self function when using another
scripts functions?
Nope, that's usually to access class members. See python self explained.
There is also more than one way to import files. See the other answer for some explanations.
I think what you are trying to ask is how to get access to global vars from on .py file without having to deal with namespaces.
In your main script, replace the call to import importedpyfile to say this instead
from importedpyfile import *
Ideally, you keep the code the way you have it. But instead, just reference those global vars with the importedpyfile namespace.
e.g.
import importedpyfile
importedpyfile.MyFunction() # calls "MyFunction" that is defined in importedpyfile.py
Python modules are not "linked" in the sense of C/C++ linking libraries into an executable. A Python import operation creates a name that refers to the imported module; without this name there is no (direct) way to access another module.
I have 3 python files.(first.py, second.py, third.py) I'm executing 2nd python file from the 1st python file. 2nd python file uses the 'import' statement to make use of 3rd python file. This is what I'm doing.
This is my code.
first.py
import os
file_path = "folder\second.py"
os.system(file_path)
second.py
import third
...
(rest of the code)
third.py (which contains ReportLab code for generating PDF )
....
canvas.drawImage('xyz.jpg',0.2*inch, 7.65*inch, width=w*scale, height=h*scale)
....
when I'm executing this code, it gives error
IOError: Cannot open resource "xyz.jpg"
But when i execute second.py file directly by writing python second.py , everything works fine..!!
Even i tried this code,
file_path = "folder\second.py"
execfile(file_path)
But it gives this error,
ImportError: No module named third
But as i stated everything works fine if i directly execute the second.py file. !!
why this is happening? Is there any better idea for executing such a kind of nested python files?
Any idea or suggestions would be greatly appreciated.
I used this three files just to give the basic idea of my structure. You can consider this flow of execution as a single process. There are too many processes like this and each file contains thousandth lines of codes. That's why i can't change the whole code to be modularize which can be used by import statement. :-(
So the question is how to make a single python file which will take care of executing all the other processes. (If we are executing each process individually, everything works fine )
This should be easy if you do it the right way. There's a couple steps that you can follow to set it up.
Step 1: Set your files up to be run or imported
#!/usr/bin/env python
def main():
do_stuff()
if __name__ == '__main__':
The __name__ special variable will contain __main__ when invoked as a script, and the module name if imported. You can use that to provide a file that can be used either way.
Step 2: Make your subdirectory a package
If you add an empty file called __init__.py to folder, it becomes a package that you can import.
Step 3: Import and run your scripts
from folder import first, second, third
first.main()
second.main()
third.main()
The way you are doing thing is invalid.
You should: create a main application, and import 1,2,3.
In 1,2,3: You should define the things as your functions. Then call them from the main application.
IMHO: I don't need that you have much code to put into separate files, you just also put them into one file with function definitions and call them properly.
I second S.Lott: You really should rethink your design.
But just to provide an answer to your specific problem:
From what I can guess so far, you have second.py and third.py in folder, along with xyz.jpg. To make this work, you will have to change your working directory first. Try it in this way in first.py:
import os
....
os.chdir('folder')
execfile('second.py')
Try reading about the os module.
Future readers:
Pradyumna's answer from here solved Moin Ahmed's second issue for me:
import sys, change "sys.path" by appending the path during run
time,then import the module that will help
[i.e. sys.path.append(execfile's directory)]