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PycURL Installation

NOTE: You need Python and libcurl installed on your system to use or build pycurl. Some RPM distributions of curl/libcurl do not include everything necessary to build pycurl, in which case you need to install the developer specific RPM which is usually called curl-dev.

Distutils

Build and install pycurl with the following commands:

(if necessary, become root)
tar -zxvf pycurl-$VER.tar.gz
cd pycurl-$VER
python setup.py install

$VER should be substituted with the pycurl version number, e.g. 7.10.5.

Note that the installation script assumes that 'curl-config' can be located in your path setting. If curl-config is installed outside your path or you want to force installation to use a particular version of curl-config, use the '--curl-config' command line option to specify the location of curl-config. Example:

python setup.py install --curl-config=/usr/local/bin/curl-config

If libcurl is linked dynamically with pycurl, you may have to alter the LD_LIBRARY_PATH environment variable accordingly. This normally applies only if there is more than one version of libcurl installed, e.g. one in /usr/lib and one in /usr/local/lib.

PycURL requires that the SSL library that it is built against is the same one libcurl, and therefore PycURL, uses at runtime. PycURL's setup.py uses curl-config to attempt to figure out which SSL library libcurl was compiled against, however this does not always work. If PycURL is unable to determine the SSL library in use it will print a warning similar to the following:

src/pycurl.c:137:4: warning: #warning "libcurl was compiled with SSL support, but configure could not determine which " "library was used; thus no SSL crypto locking callbacks will be set, which may " "cause random crashes on SSL requests" [-Wcpp]

It will then fail at runtime as follows:

ImportError: pycurl: libcurl link-time ssl backend (openssl) is different from compile-time ssl backend (none/other)

To fix this, you need to tell setup.py what SSL backend is used:

python setup.py --with-[ssl|gnutls|nss] install

easy_install / pip

easy_install pycurl
pip install pycurl

If you need to specify an alternate curl-config, it can be done via an environment variable:

export PYCURL_CURL_CONFIG=/usr/local/bin/curl-config
easy_install pycurl

The same applies to the SSL backend, if you need to specify it (see the SSL note above):

export PYCURL_SSL_LIBRARY=[openssl|gnutls|nss]
easy_install pycurl

Please note the difference in spelling that concerns OpenSSL: the command-line argument is --with-ssl, to match libcurl, but the environment variable value is "openssl".

Windows

Binary Packages

Binary packages are available in the download area for some Windows and Python version combinations. Currently, 32-bit packages are available for Python 2.6, 2.7, 3.2 and 3.3. 64-bit packages are not presently available.

In order to use the official binary packages, your installation of Python must have been compiled against the same MS Visual C++ runtime that the packages have been compiled against. Importantly, which version of MSVC is used has changed in minor releases of Python, for example between 2.7.3 and 2.7.6. As such, you may need to upgrade or downgrade your version of Python to use official PycURL packages.

Currently official PycURL packages are built against the following Python versions:

  • 2.6.6
  • 2.7.6
  • 3.2.5
  • 3.3.5

If CRTs used by PycURL and Python do not match, you will receive a message like following when trying to import pycurl module:

ImportError: DLL load failed: The specified procedure could not be found.

To troubleshoot this situation use the application profiling feature of Dependency Walker and look for msvcrt.dll variants being loaded. You may find the entire thread starting here helpful.

Installing From Source

First, you will need to obtain dependencies. These can be precompiled binaries or source packages that you are going to compile yourself.

For a minimum build you will just need libcurl source. Follow its Windows build instructions to build either a static or a DLL version of the library, then configure PycURL as follows to use it:

python setup.py --curl-dir=c:\dev\curl-7.33.0\builds\libcurl-vc-x86-release-dll-ipv6-sspi-spnego-winssl --use-libcurl-dll

Note that --curl-dir does not point to libcurl source but rather to headers and compiled libraries.

If libcurl and Python are not linked against the same exact C runtime (version number, static/dll, single-threaded/multi-threaded) you must use --avoid-stdio option (see below).

Additional Windows setup.py options:

  • --use-libcurl-dll: build against libcurl DLL, if not given PycURL will be built against libcurl statically.

  • --libcurl-lib-name=libcurl_imp.lib: specify a different name for libcurl import library. The default is libcurl.lib which is appropriate for static linking and is sometimes the correct choice for dynamic linking as well. The other possibility for dynamic linking is libcurl_imp.lib.

  • --avoid-stdio: on windows, a process and each library it is using may be linked to its own version of the C runtime (msvcrt). FILE pointers from one C runtime may not be passed to another C runtime. This option prevents direct passing of FILE pointers from Python to libcurl, thus permitting Python and libcurl to be linked against different C runtimes. This option may carry a performance penalty when Python file objects are given directly to PycURL in CURLOPT_READDATA, CURLOPT_WRITEDATA or CURLOPT_WRITEHEADER options. This option applies only on Python 2; on Python 3, file objects no longer expose C library FILE pointers and the C runtime issue does not exist. On Python 3, this option is recognized but does nothing. You can also give --avoid-stdio option in PYCURL_SETUP_OPTIONS environment variable as follows:

    PYCURL_SETUP_OPTIONS=--avoid-stdio pip install pycurl

A good setup.py target to use is bdist_wininst which produces an executable installer that you can run to install PycURL.

You may find the following mailing list posts helpful:

winbuild.py

This script is used to build official PycURL Windows packages. You can use it to build a full complement of packages with your own options or modify it to build a single package you need.

Prerequisites:

  • msysgit.
  • Appropriate Python versions installed.
  • MS Visual C++ 9/2008 for Python <= 3.2, MS Visual C++ 10/2010 for Python >= 3.3. Express versions of Visual Studio work fine for this.

winbuild.py assumes all programs are installed in their default locations, if this is not the case edit it as needed. winbuild.py itself can be run with any Python it supports - 2.6, 2.7, 3.2, 3.3 or 3.4.

Git Checkout

In order to build PycURL from a Git checkout, some files need to be generated. On Unix systems it is easiest to build PycURL with make:

make

To specify which curl or SSL backend to compile against, use the same environment variables as easy_install/pip, namely PYCURL_CURL_CONFIG and PYCURL_SSL_LIBRARY.

To generate generated files only you may run:

make gen

This might be handy if you are on Windows. Remember to run make gen whenever you change sources.

To generate documentation, run:

make docs

Generating documentation requires Sphinx to be installed.