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How to get Python relative imports right

I have a custom Python library ("common") that is being imported and used from several Python projects.
That central library has the following structure:
/common
/__init__.py
/wrapper.py
/util
/__init__.py
/misc.py
Our custom library resides in a central place /data/Development/Python, so in my Python projects I have an .env file in order to include our lib:
PYTHONPATH="/data/Development/Python"
That works fine, I can for example do something like:
from common.util import misc
However, now I want to make use of a class MyClass within common/wrapper.py from the code in common/util/misc.py. Thus I tried the following import in misc.py:
from ..wrapper import MyClass
But that leads to the following error:
Exception has occurred: ImportError
cannot import name 'MyClass'
Any ideas what I am doing wrong here?
PS: When I do an from .. import wrapper instead and then from code I use wrapper.MyClass, then it works fine. Does that make any sense?

It's finding wrapper, otherwise you'd get a different error:
>>> from wibble import myclass
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ModuleNotFoundError: No module named 'wibble'
So it seems wrapper does not contain MyClass. Typo?

"However, now I want to make use of a class MyClass within common/wrapper.py from the code in common/util/misc.py. Thus I tried the following import in misc.py:"
If you do export PYTHONPATH=~/common
In order to import MyClass you will do:
from wrapper import MyClass
Because you have added common to your root folder, utils is already in your path since it is in you root folder.
Similarly, if you wanted to import from wrapper you would do from utils.misc import ThisClass since utils.misc is already in the root folder common

Imported module cannot let me use the function it contains

I'm using a 2010 Head First Book for Python, chapter 2. I've created a module called nester, which contains the function print_lol, then made another program which should import nester, create a little list, and then call the function print_lol contained in nester. It doesn't work, tho.
import nester
cast = ["Palin", "Cleese", "Idle", "Jones", "Gilliam", "and Chapman."]
nester.print_lol(cast)
This is the program, and this is the output:
> Traceback (most recent call last):
File "<pyshell#2>", line 1, in <module>
nester.print_lol(cast)
AttributeError: module 'nester' has no attribute 'print_lol'
What's wrong with that? Why this happens? The code is exactly as in the book, same path, environment paths are ok. What's wrong?
Here is the 'nester' code, and it works properly.
def print_lol(the_list):
for each_item in the_list:
if isinstance(each_item, list):
print_lol(each_item)
else:
print(each_item)
Also, the nester it's in C:\nester. It contains setup.py, nester.py, and the installation folders and files: MANIFEST, Lib, dist, build.

Try this on your python console
dir("nester")
It should show all the available functions. You might need to make sure print_lol is in the list. Most likely, it is under some other sub-tribute. So the way you call it should be nester.some_tribute.print_lol()

Since import nester didn't throw in error, that means your script can import nester. Try (explicit function import)
from nester import print_lol
If this fails, make sure print_lol exist in nester, as in there are no spelling mistakes.

I guess I found out the answer, and it was pretty easy, but I didn't notice that until deeper research on the website with two friends here.
The module where the 'nester' class is put it's called 'nester'. So when I tried to import 'nester', I imported the module, not the class. I changed the code from the question one to:
from nester import nester
cast = ["Palin", "Cleese", "Idle", "Jones", "Gilliam", "and Chapman."]
nester.print_lol(cast)
So I import from 'nester' Module the 'nester' Class.
Pro-tip: NEVER use the same name for Module and Class.
Credits:

Python name 'os' is not defined even though it is explicitly imported

I have a module called imtools.py that contains the following function:
import os
def get_imlist(path):
return[os.path.join(path,f) for f in os.listdir(path) if f.endswith('.jpg')]
When I attempt to call the function get_imlist from the console using import imtools and imtools.get_imlist(path), I receive the following error:
Traceback (most recent call last):
File "<input>", line 1, in <module>
File "C:\...\PycharmProjects\first\imtools.py", line 5, in get_imlist
NameError: name 'os' is not defined
I'm new at Python and I must be missing something simple here, but cannot figure this out. If I define the function at the console it works fine. The specific history of this module script is as follows: initially it was written without the import os statement, then after seeing the error above the import os statement was added to the script and it was re-saved. The same console session was used to run the script before and after saving.

Based on small hints, I'm going to guess that your code didn't originally have the import os line in it but you corrected this in the source and re-imported the file.
The problem is that Python caches modules. If you import more than once, each time you get back the same module - it isn't re-read. The mistake you had when you did the first import will persist.
To re-import the imtools.py file after editing, you must use reload(imtools).

Same problem is with me I am also trying to follow the book of Programming Computer Vision with Python by Jan Erik Solem" [http://programmingcomputervision.com/]. I tried to explore on internet to see the problem but I did not find any valuable solution but I have solved this problem by my own effort.
First you just need to place the 'imtools.py' into the parent folder of where your Python is installed like C:\Python so place the file into that destination and type the following command:
from PIL import Image
from numpy import *
from imtools import *
Instead of typing the code with imtools.get_imlist() you just to remove the imtools from the code like:
get_imlist()
This may solve your problem as I had found my solution by the same technique I used.

NameError when importing a dict

I've got a script where I want to import a dict from a file and then use it to execute functions.
The file codes.py is as follows:
rf_433mhz = {
"0x471d5c" : sensor_LaundryDoor,
}
And the file it's using is as follows:
#!/usr/bin/python
import mosquitto
import json
import time
def sensor_LaundryDoor():
print "Laundry Door Opened"
mqttc.publish("actuators", json.dumps(["switch_HallLight", "on"]))
from codes import rf_433mhz
but I'm getting a NameError.
Traceback (most recent call last):
File "sensors.py", line 11, in <module>
from codes import rf_433mhz
File "/root/ha/modules/processing/codes.py", line 2, in <module>
"0x471d5c" : sensor_LaundryDoor,
NameError: name 'sensor_LaundryDoor' is not defined
Is there any way to do what I'm trying to do? It seems to be getting stuck on not having the function inside codes.py
I'm trying to call sensor_LaundryDoor() as follows
def on_message(msg):
inbound = json.loads(msg.payload)
medium = inbound[0]
content = inbound[1]
if str(medium) == "433mhz":
try:
rf_433mhz[str(content)]()
except:
print "Sorry code " + content + " is not setup"

import isn't include. It won't dump the source code of codes.py into your script; rather, it runs codes.py in its own namespace, almost like a separate script, and then assigns either the module object or specific module contents to names in the namespace the import is in. In the namespace of codes.py, there is no sensor_LaundryDoor variable.
The way you're dividing the code into modules isn't very useful. To understand codes.py, you need to understand the other file to know what sensor_LaundryDoor is. To understand the other file, you need to understand codes.py to know what you're importing. This circular dependency would negate most of the benefit of modularizing your code even if it wasn't an error. Reorganize your code to fix the circular dependency, and you'll probably fix the NameError as well.

The problem is that in your dictionary that you're importing, you're setting the value of 0x471d5c to a variable that was either not defined, or not defined in that scope.
An example of this would be like:
Codes.py
#!/usr/bin/python
sensor_LaundryDoor = 'foo'
rf_433mhz = {
"0x471d5c" : sensor_LaundryDoor,
}
Main files
#!/usr/bin/python
from test import rf_433mhz
print rf_433mhz["0x471d5c"]

There are hacky ways to solve this but it looks like the real issue is that you're trying to write C-style code in Python. The Python way to do things would be to import sensor_LaundryDoor in codes.py before using it, and if this introduces a circular reference then that's a design issue.
Maybe you need three modules, events.py with your main loop which imports the dict from codes.py which imports the functions from sensors.py.

python interactive mode module import issue

I believe I have what would be called a scope issue, perhaps name space. Not too sure I'm new to python.
I'm trying to make a module that will search through a list using regular expressions. I'm sure there is a better way of doing it but this error that I'm getting is bugging me and I want to understand why.
here's my code:
class relist(list):
def __init__(self, l):
list.__init__(self, l)
def __getitem__(self, rexp):
r = re.compile(rexp)
res = filter(r.match, self)
return res
if __name__ == '__main__':
import re
listl = [x+y for x in 'test string' for y in 'another string for testing']
print(listl)
test = relist(listl)
print('----------------------------------')
print(test['[s.]'])
When I run this code through the command line it works the way I expect it to; however when I run it through python interactive mode I get the error
>>> test['[s.]']
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "relist.py", line 8, in __getitem__
r = re.compile(rexp)
NameError: global name 're' is not defined
While in the interactive mode I do import re and I am able to use the re functions, but for some reason when I'm trying to execute the module it doesn't work.
Do I need to import re into the scope of the class? I wouldn't think so because doesn't python search through other scopes if it's not found in the current one?
I appreciate your help, and if there is a better way of doing this search I would be interested in knowing. Thanks

Move the "import re" out of the bottom "if..." to the top of the file:
import re
class ....
You're only importing the re module when run as a program, not imported as a module.
(Also, Python style prefers upper-case class names.)

Python does not run anything "ahead of time"; it runs code when it encounters it. The only thing that's done "ahead of time" is to translate the source code into bytecode.
When you import the module, __name__ is the name of the module, rather than __main__. Thus, the code in the if block at the end is not executed, and re is not imported. When you then attempt to use the class, the name re is looked up right then, when it's needed (to access re.compile), and not found (because the module wasn't imported earlier).