问题描述

我的 ubuntu 是 14.04 LTS.

My ubuntu is 14.04 LTS.

当我安装密码学时，错误是:

When I install cryptography, the error is:

Installing egg-scripts.
uses namespace packages but the distribution does not require setuptools.
Getting distribution for 'cryptography==0.2.1'.

no previously-included directories found matching 'documentation/_build'
zip_safe flag not set; analyzing archive contents...
six: module references __path__

Installed /tmp/easy_install-oUz7ei/cryptography-0.2.1/.eggs/six-1.10.0-py2.7.egg
Searching for cffi>=0.8
Reading https://pypi.python.org/simple/cffi/
Best match: cffi 1.5.0
Downloading https://pypi.python.org/packages/source/c/cffi/cffi-1.5.0.tar.gz#md5=dec8441e67880494ee881305059af656
Processing cffi-1.5.0.tar.gz
Writing /tmp/easy_install-oUz7ei/cryptography-0.2.1/temp/easy_install-Yf2Yl3/cffi-1.5.0/setup.cfg
Running cffi-1.5.0/setup.py -q bdist_egg --dist-dir /tmp/easy_install-oUz7ei/cryptography-0.2.1/temp/easy_install-Yf2Yl3/cffi-1.5.0/egg-dist-tmp-A2kjMD
c/_cffi_backend.c:15:17: fatal error: ffi.h: No such file or directory
 #include <ffi.h>
                 ^
compilation terminated.
error: Setup script exited with error: command 'x86_64-linux-gnu-gcc' failed with exit status 1
An error occurred when trying to install cryptography 0.2.1. Look above this message for any errors that were output by easy_install.
While:
  Installing egg-scripts.
  Getting distribution for 'cryptography==0.2.1'.
Error: Couldn't install: cryptography 0.2.1

我不知道为什么它失败了.是什么原因.在ubuntu系统上安装有什么必要的吗?

I don't know why it was failed. What is the reason. Is there something necessary when install it on ubuntu system?

推荐答案

答案在 cryptography 的 安装部分 这几乎反映了 Angelos 的回答:

The answer is on the docs of cryptography's installation section which pretty much reflects Angelos' answer:

引用它:

对于 Debian 和 Ubuntu，以下命令将确保已安装所需的依赖项:

For Debian and Ubuntu, the following command will ensure that the required dependencies are installed:

$ sudo apt-get install build-essential libssl-dev libffi-dev python-dev

对于 Fedora 和 RHEL 衍生产品，以下命令将确保已安装所需的依赖项:

For Fedora and RHEL-derivatives, the following command will ensure that the required dependencies are installed:

$ sudo yum install gcc libffi-devel python-devel openssl-devel

您现在应该能够使用平常的

You should now be able to build and install cryptography with the usual

$ pip install cryptography

如果您使用的是 Python 3，请在第一个命令中使用 python3-dev 而不是 python-dev.(感谢@chasmani)

If you're using Python 3, please use python3-dev instead of python-dev in the first command. (thanks to @chasmani)

如果您在 Ubuntu 18.04 上安装它，请在第一个命令中使用 libssl1.0 而不是 libssl-dev.(感谢@pobe)

If you're installing this on Ubuntu 18.04, please use libssl1.0 instead of libssl-dev in the first command. (thanks to @pobe)

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