I am using Ubuntu and have installed Python 2.7.5 and 3.4.0. In Python 2.7.5 I am able to successfully assign a variable x = Value('i', 2), but not in 3.4.0. I am getting:
Traceback (most recent call last): File "<stdin>", line 1, in <module> File "/usr/local/lib/python3.4/multiprocessing/context.py", line 132, in Value from .sharedctypes import Value File "/usr/local/lib/python3.4/multiprocessing/sharedctypes.py", line 10, in <
module> import ctypes File "/usr/local/lib/python3.4/ctypes/__init__.py", line 7, in <module> from _ctypes import Union, Structure, Array
ImportError: No module named '_ctypes'I just updated to 3.3.2 through installing the source of 3.4.0. It installed in /usr/local/lib/python3.4.
Did I update to Python 3.4 correctly?
One thing I noticed that Python 3.4 is installed in usr/local/lib, while Python 3.3.2 is still installed in usr/lib, so it was not overwritten.
419 Answers
Installing libffi-dev and re-installing python3.7 fixed the problem for me.
to cleanly build py 3.7 libffi-dev is required or else later stuff will fail
If using RHEL/Fedora:
yum install libffi-develor
sudo dnf install libffi-develIf using Debian/Ubuntu:
sudo apt-get install libffi-devOn a fresh Debian image, cloning and running:
sudo apt-get update
sudo apt-get upgrade
sudo apt-get dist-upgrade
sudo apt-get install build-essential python-dev python-setuptools python-pip python-smbus
sudo apt-get install libncursesw5-dev libgdbm-dev libc6-dev
sudo apt-get install zlib1g-dev libsqlite3-dev tk-dev
sudo apt-get install libssl-dev openssl
sudo apt-get install libffi-devNow execute the configure file cloned above:
./configure
make # alternatively `make -j 4` will utilize 4 threads
sudo make altinstallGot 3.7 installed and working for me.
SLIGHT UPDATE
Looks like I said I would update this answer with some more explanation and two years later I don't have much to add.
- this SO post explains why certain libraries like
python-devmight be necessary. - this SO post explains why one might use the
altinstallas opposed toinstallargument in the make command.
Aside from that I guess the choice would be to either read through the cpython codebase looking for #include directives that need to be met, but what I usually do is keep trying to install the package and just keep reading through the output installing the required packages until it succeeds.
Reminds me of the story of the Engineer, the Manager and the Programmer whose car rolls down a hill.
9If you use pyenv and get error "No module named '_ctypes'" (like i am) on Debian/Raspbian/Ubuntu you need to run this commands:
sudo apt-get install libffi-dev
pyenv uninstall 3.7.6
pyenv install 3.7.6Put your version of python instead of 3.7.6
8Detailed steps to install Python 3.7 in CentOS or any redhat linux machine:
- Download Python from
- Extract the content in new folder
- Open Terminal in the same directory
- Run below code step by step :
3sudo yum -y install gcc gcc-c++ sudo yum -y install zlib zlib-devel sudo yum -y install libffi-devel ./configure make make install
Thought I'd add the Centos installs:
sudo yum -y install gcc gcc-c++
sudo yum -y install zlib zlib-devel
sudo yum -y install libffi-devel Check python version:
python3 -V
Create virtualenv:
virtualenv -p python3 venv
This solved the same error for me on Debian:
sudo apt-get install libffi-devand compile again
Reference: issue31652
On my Ubuntu 18.04 machine, I had the common problem of python not finding _ctypes with the pyenv installed python.
In my case libffi-dev was already installed. Installing cpython from source, as suggested by @MikeiLL, didn't help either.
Turned out to be an homebrew issue.
ajkerrigans suggested solution on pyenvs github issues solved this problem for me.
Solution summary: Tell pyenv to build Python using the Homebrew-managed GCC, with a command like:
CC="$(brew --prefix gcc)/bin/gcc-11" \
pyenv install --verbose 3.10.0This assumes that any build dependencies have also been installed via Homebrew as specified in the pyenv wiki. As of this writing, that looks like this for Homebrew on Linux:
brew install bzip2 libffi libxml2 libxmlsec1 openssl readline sqlite xz zlibNone of the solution worked. You have to recompile your python again; once all the required packages were completely installed.
Follow this:
- Install required packages
- Run
./configure --enable-optimizations
I run into this error when I tried to install Python 3.7.3 in Ubuntu 18.04 with next command: $ pyenv install 3.7.3.
Installation succeeded after running $ sudo apt-get update && sudo apt-get install libffi-dev (as suggested here).
The issue was solved there.
Based on this answer, just copy-paste into the terminal.
First run:sudo apt-get -y update
then:
sudo apt-get -y upgrade
sudo apt-get -y dist-upgrade
sudo apt-get -y install build-essential python-dev python-setuptools python-pip python-smbus
sudo apt-get -y install libncursesw5-dev libgdbm-dev libc6-dev
sudo apt-get -y install zlib1g-dev libsqlite3-dev tk-dev
sudo apt-get -y install libssl-dev openssl
sudo apt-get -y install libffi-devPS: You can just copy-paste the whole chunk into the terminal in one go.
In my case what was causing all sorts of Python installation issues including the one having to do with _ctypes and libffi was Homebrew on Linux / Linuxbrew. pyenv was happy again once brew was no longer in the $PATH.
Refer to this thread or this thread, for customized installation of libffi, it is difficult for Python3.7 to find the library location of libffi. An alternative method is to set the CONFIGURE_LDFLAGS variable in the Makefile, for example CONFIGURE_LDFLAGS="-L/path/to/libffi-3.2.1/lib64".
My solution: Installing libffi-dev with apt-get didn't help. But this helped: Installing libffi from source and then installing Python 3.8 from source.
My configuration: Ubuntu 16.04 LTS Python 3.8.2
Step by step:
I got the error message "ModuleNotFoundError: No module named '_ctypes'" when starting the debugger from Visual Studio Code, and when running python3 -c "import sklearn; sklearn.show_versions()".
- download libffi v3.3 from
- install libtool:
sudo apt-get install libtoolThe file README.md from libffi mentions that autoconf and automake are also necessary. They were already installed on my system. - configure libffi without docs:
./configure --disable-docs
make check
sudo make install
- download python 3.8 from
./configuremakemake testmake install
After that my python installation could find _ctypes.
1CentOS without root
Install libffi-3.2 (Do NOT use libffi-3.3)
wget ftp://
tar -xzf libffi-3.2.tar.gz
cd libffi-3.2/
./configure --prefix=$YOUR_LIBFFI_DIR
make && make installInstall Python3
./configure --prefix=$YOUR_PATH/python/3.7.10 LDFLAGS=-L${YOUR_LIBFFI_DIR}/lib64 PKG_CONFIG_PATH=${YOUR_LIBFFI_DIR}/lib/pkgconfig --enable-shared
make && make install
Thanks for JohnWSteill
I was having the same problem. None of the above solutions worked for me. The key challenge was that I didn't have the root access. So, I first download the source of libffi. Then I compiled it with usual commands:
./configure --prefix=desired_installation_path_to_libffi
make Then I recompiled python using
./configure --prefix=/home/user123/Softwares/Python/installation3/ LDFLAGS='-L/home/user123/Softwares/library/libffi/installation/lib64'
make
make installIn my case, 'home/user123/Softwares/library/libffi/installation/lib64' is path to LIBFFI installation directory where libffi.so is located. And, /home/user123/Softwares/Python/installation3/ is path to Python installation directory. Modify them as per your case.
If you don't mind using Miniconda, the necessary external libraries and _ctypes are installed by default. It does take more space and may require using a moderately older version of Python (e.g. 3.7.6 instead of 3.8.2 as of this writing).
You have to load the missing php3 (Python3) modules from the package manager.
If you have Ubuntu I recommend the Synaptic Package Manager:
sudo apt-get install synapticThere you can simply search for the missing modules. search for ctypes and install all the packages. Then go to your Python dir and do
./configure
make install.This should solve your problem.
How to install Python from source without libffi in /usr/local?
- Download libffi from github and install to
/path/to/local - Download python source code and compile with the following configuration:
export PKG_CONFIG_PATH=/path/to/local/lib/pkgconfig
./configure --prefix=/path/to/python \ LDFLAGS='-L/path/to/local/lib -Wl,-R/path/to/local/lib' \ --enable-optimizations
make
make installIf you are doing something nobody here will listen you about because "you're doing it the wrong way", but you have to do it "the wrong way" for reasons too asinine to explain and also beyond your ability to control, you can try this:
Get libffi and install it into your user install area the usual way.
git clone
cd libffi
./configure --prefix=path/to/your/install/root
make
make installThen go back to your Python 3 source and find this part of the code in setup.py at the top level of the python source directory
ffi_inc = [sysconfig.get_config_var("LIBFFI_INCLUDEDIR")] if not ffi_inc or ffi_inc[0] == '': ffi_inc = find_file('ffi.h', [], inc_dirs) if ffi_inc is not None: ffi_h = ffi_inc[0] + '/ffi.h' if not os.path.exists(ffi_h): ffi_inc = None print('Header file {} does not exist'.format(ffi_h)) ffi_lib = None if ffi_inc is not None: for lib_name in ('ffi', 'ffi_pic'): if (self.compiler.find_library_file(lib_dirs, lib_name)): ffi_lib = lib_name break ffi_lib="ffi" # --- AND INSERT THIS LINE HERE THAT DOES NOT APPEAR --- if ffi_inc and ffi_lib: ext.include_dirs.extend(ffi_inc) ext.libraries.append(ffi_lib) self.use_system_libffi = Trueand add the line I have marked above with the comment. Why it is necessary, and why there is no way to get configure to respect '--without-system-ffi` on Linux platforms, perhaps I will find out why that is "unsupported" in the next couple of hours, but everything has worked ever since. Otherwise, best of luck... YMMV.
WHAT IT DOES: just overrides the logic there and causes the compiler linking command to add "-lffi" which is all that it really needs. If you have the library user-installed, it is probably detecting the headers fine as long as your PKG_CONFIG_PATH includes path/to/your/install/root/lib/pkgconfig.
