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ModuleNotFoundError: No module named 'cryptography'

these are the Error messages I am geeting on running any of my project modules.
Traceback (most recent call last):
File "C:\Users\hsnl\BlockchainCodesTutor\Wallet.py", line 3, in <module>
import Transactions
File "C:\Users\hsnl\BlockchainCodesTutor\Transactions.py", line 2, in <module>
import Signatures
File "C:\Users\hsnl\BlockchainCodesTutor\Signatures.py", line 2, in <module>
import cryptography
ModuleNotFoundError: No module named 'cryptography'
I have already installed the cryptography module and was working perfectly until today I start getting this message that " No module named 'cryptography'".
I have again installed the cryptography as well as pip package but still showing the same error.

There might be loose versions running on your system. Please try the following:
python -m pip uninstall cryptography
python -m pip install cryptography
You can also check out this with python -m to make sure you are not using a loose pip.

You might not have cryptogtaphy installed correctly. I see you are using windows. Open commandline as an administrator and run pip install cryptography again. Enshure that the installation finishes without any errors and consider to restart your python interpreter after installation.
For further help you should post more details like the output of pip and your code leading to the error, so a more detailed answer for your problem can be given.

Try download cryptography whl from here.
Then use pip install cryptography-XXX.whl
For example:
pip install cryptography-3.3.1-cp36-abi3-win_amd64.whl
And now just supports python2.7 and python3.6.

Install via pacman to specific version of Python

The default Python version for MSYS2 seems to be 3.8. I need to use 3.7 at the moment because I have to use PyInstaller and it is not currently compatible with 3.8 in MSYS2. I can download the earlier version of Python from http://repo.msys2.org/ and install it using pacman. With a fresh install of MSYS2 I run the following commands:
pacman -S glib2-devel
pacman -U python-3.7.4-1-x86_64.pkg.tar.xz
pacman -S python-pip
pacman -S python-setuptools
If I try to run a python script I am met with an error:
File "setup.py", line 15, in <module>
from setuptools import setup
ModuleNotFoundError: No module named 'setuptools'
This is due to the fact that everything installed after Python is actually installing in the default Python 3.8 location rather than 3.7:
C:\msys64\usr\lib\python3.8\site-packages
If I copy and paste the contents of site-packages into Python 3.7 and then try running a script I get the error:
File "setup.py", line 15, in <module>
from setuptools import setup
File "/usr/lib/python3.7/site-packages/setuptools/__init__.py", line 19, in <module>
from setuptools.dist import Distribution
File "/usr/lib/python3.7/site-packages/setuptools/dist.py", line 34, in <module>
from setuptools import windows_support
File "/usr/lib/python3.7/site-packages/setuptools/windows_support.py", line 2, in <module>
import ctypes
File "/usr/lib/python3.7/ctypes/__init__.py", line 7, in <module>
from _ctypes import Union, Structure, Array
ImportError: No such file or directory
Which is supposed to be resolved via libffi, which was installed prior to Python, but likely does not go to a location that 3.7 can recognize?
Is there a way to set a specific version of Python as the default in MSYS2? Perhaps a path that can be set in the .bashrc file? I tried to set PYTHONPATH in there to Python 3.7 but it didn't make a difference as to where the packages ended up being installed to.

Go to the following URL...
https://repo.msys2.org/msys/x86_64/
Look for the version of the package you need and download it. Use
pacman -U pkgname
To install it...
The reason I know this is because gcc11 on MSYS is non-functional... it produces programs which crash and say
"During startup your program exited with code..." mentioned here:
During startup program exited with code 0xc0000139
The only workaround is to downgrade to the previous compiler which does work or use clang, which was not an option for me.

Trying to use an old version of Python is probably possible, but I think it will be very difficult. You would need to make sure all the other installed packages are compatible.
I am using PyInstaller with Python 3.8 in MSYS2 without issues. I would recommend trying to work through any issues with that, instead of trying to use older versions of packages.

How do I update python on my Raspberry Pi to at least 3.6?

As some brief background information: I was origianlly trying to use Miniconda (with conda) to install dependencies that I need for my project on my Raspberry Pi. After trying to use Conda to install the SimpleAudio package, I got an error saying that it did not exist, therefore I proceeded to install this through Pip. Pip found the correct package although I get the following error message:
pi#raspberrypi:~ $ pip install simpleaudio
Traceback (most recent call last):
File "/home/pi/miniconda3/bin/pip", line 7, in <module>
from pip._internal.cli.main import main
File "/home/pi/miniconda3/lib/python3.4/site-packages/pip/_internal/cli/main.py", line 10, in <module>
from pip._internal.cli.autocompletion import autocomplete
File "/home/pi/miniconda3/lib/python3.4/site-packages/pip/_internal/cli/autocompletion.py", line 9, in <module>
from pip._internal.cli.main_parser import create_main_parser
File "/home/pi/miniconda3/lib/python3.4/site-packages/pip/_internal/cli/main_parser.py", line 7, in <module>
from pip._internal.cli import cmdoptions
File "/home/pi/miniconda3/lib/python3.4/site-packages/pip/_internal/cli/cmdoptions.py", line 28, in <module>
from pip._internal.models.target_python import TargetPython
File "/home/pi/miniconda3/lib/python3.4/site-packages/pip/_internal/models/target_python.py", line 4, in <module>
from pip._internal.utils.misc import normalize_version_info
File "/home/pi/miniconda3/lib/python3.4/site-packages/pip/_internal/utils/misc.py", line 20, in <module>
from pip._vendor import pkg_resources
File "/home/pi/miniconda3/lib/python3.4/site-packages/pip/_vendor/pkg_resources/__init__.py", line 92, in <module>
raise RuntimeError("Python 3.5 or later is required")
RuntimeError: Python 3.5 or later is required
It seems I need to update Python, although when I print the verion on Spyder IDE, it says I am already using 3.7.
Have I caused some sort of mismatch between what version my IDE is using and what the default process the terminal uses to look up the version? I noticed that it is looking for the Python version under Miniconda. If I can update If so is there a fix for this?
Please as me for more information if required (I am fairly new to stack overflow).

UPDATE:
I have been able to install the updated version of Python to 3.6 using the following instructions:
https://stackoverflow.com/a/56852714/12361146
This generally solves the scope of this question in terms of how I update Python, but I am still confused as to why Spyder IDE uses a more up-to-date version of Python whereas the terminal shows otherwise.

To answer the question of why Spyder reports a more up-to-date version of Python, here's the reason. The default versions of Python that are installed with Raspbian are 2.7 and 3.5, located in the /usr/bin/ directory. When you install Spyder, however (either independently, or more commonly, using conda), it includes its own installation of Python, which it is configured to use in the IDE, and which is located in a different directory. Hence when you compare the versions, first by entering python3 --version on the command line, and then print(sys.executable) from the Spyder IDE, they're different.
Now the issue with using pip alongside conda for updating the Spyder installation of Python is that it has the potential to mess it up quite badly, so avoid that unless you really know what you're doing. From code you posted above, you have avoided that, though, since that will have impacted the default Raspbian installation of Python, not the Spyder one. Upgrading the latter version should be done using Conda, not pip.
Hopefully you're now all up and running.

You can install newer versions of python using the package manager apt or apt-get.
Start by getting up-to-date package definitions.
$ sudo apt-get update
Then you can show details about the python3 package.
$ apt-cache show python3
When I run that now I get "Version: 3.7.3-1".
To install the python3 package and all its dependencies.
$ sudo apt-get install python3
You will still need to type python3 and pip3 when you run the commands because you are not replacing the built-in python 2.7.
Try these commands to see what you get
$ python --version
$ python3 --version
If you want to change the default python to python3 then have a look at this answer How to change the default python version in Raspberry Pi

ModuleNotFoundError: No module named 'ruamel'

I'm using a Kubernetes inventory builder script found here: https://github.com/kubernetes-sigs/kubespray/blob/master/contrib/inventory_builder/inventory.py
On line 36, the ruamel YML library is imported using the code from ruamel.yaml import YAML. This library can be found here: https://pypi.org/project/ruamel.yaml/
On my OSX device (Mojave 10.14.3), if I run pip list, I can clearly see the most up to date version of ruamel.yaml:
If I run pip show ruamel.yaml, I get the following output:
I'm running the script with this command: CONFIG_FILE=inventory/mycluster/hosts.ini python3 contrib/inventory_builder/inventory.py 10.0.0.1 10.0.0.2 10.0.0.4 10.0.0.5
Bizarrely, it returns the following error:
Traceback (most recent call last):
File "contrib/inventory_builder/inventory.py", line 36, in <module>
from ruamel.yaml import YAML
ModuleNotFoundError: No module named 'ruamel'
I have very little experience with Python, so don't understand how this could be failing. Have I installed the library incorrectly or something? From the documentation on the ruamel.yml project page, it looks like the script is calling the library as it should be.
Thanks in advance

In my case, I was installing this with pip3 install ruamel.yaml, and it was puting the package in /usr/local/lib/python3.9/site-packages/, but the python3 binary on the machine was pinned to Python 3.7, so trying to import that module was sending the ModuleNotFoundError message.
What helped to fix this, was to install the module with python3 -m pip install ruamel.yaml, running pip via the python3 binary makes sure it runs on the same version, in this case 3.7, and gets installed via the correct version number site-packages.

pip is set to point to the Python 2 installation. To install the library under Python 3, do pip3 install ruamel.yml.

you're using python 3 and want to use the package that is with python 2. Go to the directory where your python 3 is, navigate to Scripts and use the pip in there to install the needed library.

This helped me (adding version number to python):
CONFIG_FILE=inventory/mycluster/hosts.yaml python3.6 contrib/inventory_builder/inventory.py ${IPS[#]}

[python 3.10.x].
There is no package called ruamel.yaml
what worked is pip install ruamel-yaml

no module librepo after installing pytorch on fedora27

I had to install pytorch with conda, and next I had this error when trying to upgrade system :
sudo dnf upgrade
Traceback (most recent call last):
File "/bin/dnf", line 57, in <module>
from dnf.cli import main
File "/usr/lib/python3.6/site-packages/dnf/__init__.py", line 31, in <module>
import dnf.base
File "/usr/lib/python3.6/site-packages/dnf/base.py", line 26, in <module>
from dnf.comps import CompsQuery
File "/usr/lib/python3.6/site-packages/dnf/comps.py", line 29, in <module>
import dnf.util
File "/usr/lib/python3.6/site-packages/dnf/util.py", line 32, in <module>
import librepo
ModuleNotFoundError: No module named 'librepo'
I saw some answer that uses yum-deprecated for re install python, but it seems I don't have it on my machine. I don't want to reinstall linux another time, and I'm searching for kind an answer for that problem.
When installing pytorch via conda, it also installed cuda. Maybe it can be a problem ?
Before this, I remember (not sure, but kind of) I was running with python2.7 by default, and now it is python 3.6..

First the magic one-liner to fix things:
echo 'import sys;sys.path += ["/usr/lib64/python3.6/site-packages/", "/usr/lib64/python3.6/"]' | sudo tee /usr/lib/python3.6/site-packages/lib64.pth
I got the same error after using conda to install jupyterlab. For some reason conda installed its own version of python which shadows fedora's one. Conda's python searches libraries from /usr/lib/ while fedora's also searches /usr/lib64/. On most linux distros /usr/lib/ is a link for /usr/lib64/ or the other way so either one can be used. librepo is installed in /usr/lib64/.
My conclusions:
Fedora is not completely compatible with conda.
Fedora bug reports get closed as duplicate with links to obviously unrelated reports.

I have stumbled upon the same issue in Fedora 28. I used anaconda as root to update packages system wide, and this broke dnf with the message
ModuleNotFoundError: No module named 'librepo'
yum-deprecated did not work, although Fedora installed it for me after automatically querying for it (a bit strange that this worked since dnf and yum did not work).
In order to fix the issue, I deleted the existing libpython, downloaded the python3 and python3-lib rpms from rpmfind, and installed the new rpms
rm -rf /usr/lib/libpython3*.*
rpm -iv --replacepkgs python3-3.6.6-1.fc28.x86_64.rpm
rpm -iv --replacepkgs python3-libs-3.6.6-1.fc28.x86_64.rpm
Now I know it is better to use pip than anaconda system wide.