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Diffstat (limited to 'Doc/library/venv.rst')
| -rw-r--r-- | Doc/library/venv.rst | 134 |
1 files changed, 76 insertions, 58 deletions
diff --git a/Doc/library/venv.rst b/Doc/library/venv.rst index af4a6d1..6bf26ff 100644 --- a/Doc/library/venv.rst +++ b/Doc/library/venv.rst @@ -31,44 +31,50 @@ Creating virtual environments .. _venv-def: -.. note:: A virtual environment (also called a ``venv``) is a Python - environment such that the Python interpreter, libraries and scripts - installed into it are isolated from those installed in other virtual - environments, and (by default) any libraries installed in a "system" Python, - i.e. one which is installed as part of your operating system. +.. note:: A virtual environment is a Python environment such that the Python + interpreter, libraries and scripts installed into it are isolated from those + installed in other virtual environments, and (by default) any libraries + installed in a "system" Python, i.e., one which is installed as part of your + operating system. - A venv is a directory tree which contains Python executable files and - other files which indicate that it is a venv. + A virtual environment is a directory tree which contains Python executable + files and other files which indicate that it is a virtual environment. Common installation tools such as ``Setuptools`` and ``pip`` work as - expected with venvs - i.e. when a venv is active, they install Python - packages into the venv without needing to be told to do so explicitly. - - When a venv is active (i.e. the venv's Python interpreter is running), the - attributes :attr:`sys.prefix` and :attr:`sys.exec_prefix` point to the base - directory of the venv, whereas :attr:`sys.base_prefix` and - :attr:`sys.base_exec_prefix` point to the non-venv Python installation - which was used to create the venv. If a venv is not active, then - :attr:`sys.prefix` is the same as :attr:`sys.base_prefix` and - :attr:`sys.exec_prefix` is the same as :attr:`sys.base_exec_prefix` (they - all point to a non-venv Python installation). - - When a venv is active, any options that change the installation path will be - ignored from all distutils configuration files to prevent projects being - inadvertently installed outside of the virtual environment. - - When working in a command shell, users can make a venv active by running an - ``activate`` script in the venv's executables directory (the precise filename - is shell-dependent), which prepends the venv's directory for executables to - the ``PATH`` environment variable for the running shell. There should be no - need in other circumstances to activate a venv -- scripts installed into - venvs have a shebang line which points to the venv's Python interpreter. This - means that the script will run with that interpreter regardless of the value - of ``PATH``. On Windows, shebang line processing is supported if you have the - Python Launcher for Windows installed (this was added to Python in 3.3 - see - :pep:`397` for more details). Thus, double-clicking an installed script in - a Windows Explorer window should run the script with the correct interpreter - without there needing to be any reference to its venv in ``PATH``. + expected with virtual environments. In other words, when a virtual + environment is active, they install Python packages into the virtual + environment without needing to be told to do so explicitly. + + When a virtual environment is active (i.e., the virtual environment's Python + interpreter is running), the attributes :attr:`sys.prefix` and + :attr:`sys.exec_prefix` point to the base directory of the virtual + environment, whereas :attr:`sys.base_prefix` and + :attr:`sys.base_exec_prefix` point to the non-virtual environment Python + installation which was used to create the virtual environment. If a virtual + environment is not active, then :attr:`sys.prefix` is the same as + :attr:`sys.base_prefix` and :attr:`sys.exec_prefix` is the same as + :attr:`sys.base_exec_prefix` (they all point to a non-virtual environment + Python installation). + + When a virtual environment is active, any options that change the + installation path will be ignored from all distutils configuration files to + prevent projects being inadvertently installed outside of the virtual + environment. + + When working in a command shell, users can make a virtual environment active + by running an ``activate`` script in the virtual environment's executables + directory (the precise filename is shell-dependent), which prepends the + virtual environment's directory for executables to the ``PATH`` environment + variable for the running shell. There should be no need in other + circumstances to activate a virtual environment—scripts installed into + virtual environments have a "shebang" line which points to the virtual + environment's Python interpreter. This means that the script will run with + that interpreter regardless of the value of ``PATH``. On Windows, "shebang" + line processing is supported if you have the Python Launcher for Windows + installed (this was added to Python in 3.3 - see :pep:`397` for more + details). Thus, double-clicking an installed script in a Windows Explorer + window should run the script with the correct interpreter without there + needing to be any reference to its virtual environment in ``PATH``. .. _venv-api: @@ -83,7 +89,8 @@ mechanisms for third-party virtual environment creators to customize environment creation according to their needs, the :class:`EnvBuilder` class. .. class:: EnvBuilder(system_site_packages=False, clear=False, \ - symlinks=False, upgrade=False, with_pip=False) + symlinks=False, upgrade=False, with_pip=False, \ + prompt=None) The :class:`EnvBuilder` class accepts the following keyword arguments on instantiation: @@ -107,9 +114,16 @@ creation according to their needs, the :class:`EnvBuilder` class. installed in the virtual environment. This uses :mod:`ensurepip` with the ``--default-pip`` option. + * ``prompt`` -- a String to be used after virtual environment is activated + (defaults to ``None`` which means directory name of the environment would + be used). + .. versionchanged:: 3.4 Added the ``with_pip`` parameter + .. versionadded:: 3.6 + Added the ``prompt`` parameter + Creators of third-party virtual environment tools will be free to use the provided ``EnvBuilder`` class as a base class. @@ -219,7 +233,7 @@ An example of extending ``EnvBuilder`` -------------------------------------- The following script shows how to extend :class:`EnvBuilder` by implementing a -subclass which installs setuptools and pip into a created venv:: +subclass which installs setuptools and pip into a created virtual environment:: import os import os.path @@ -233,12 +247,12 @@ subclass which installs setuptools and pip into a created venv:: class ExtendedEnvBuilder(venv.EnvBuilder): """ This builder installs setuptools and pip so that you can pip or - easy_install other packages into the created environment. + easy_install other packages into the created virtual environment. :param nodist: If True, setuptools and pip are not installed into the - created environment. + created virtual environment. :param nopip: If True, pip is not installed into the created - environment. + virtual environment. :param progress: If setuptools or pip are installed, the progress of the installation can be monitored by passing a progress callable. If specified, it is called with two @@ -264,10 +278,10 @@ subclass which installs setuptools and pip into a created venv:: def post_setup(self, context): """ Set up any packages which need to be pre-installed into the - environment being created. + virtual environment being created. - :param context: The information for the environment creation request - being processed. + :param context: The information for the virtual environment + creation request being processed. """ os.environ['VIRTUAL_ENV'] = context.env_dir if not self.nodist: @@ -301,7 +315,7 @@ subclass which installs setuptools and pip into a created venv:: fn = os.path.split(path)[-1] binpath = context.bin_path distpath = os.path.join(binpath, fn) - # Download script into the env's binaries folder + # Download script into the virtual environment's binaries folder urlretrieve(url, distpath) progress = self.progress if self.verbose: @@ -313,7 +327,7 @@ subclass which installs setuptools and pip into a created venv:: else: sys.stderr.write('Installing %s ...%s' % (name, term)) sys.stderr.flush() - # Install in the env + # Install in the virtual environment args = [context.env_exe, fn] p = Popen(args, stdout=PIPE, stderr=PIPE, cwd=binpath) t1 = Thread(target=self.reader, args=(p.stdout, 'stdout')) @@ -332,10 +346,10 @@ subclass which installs setuptools and pip into a created venv:: def install_setuptools(self, context): """ - Install setuptools in the environment. + Install setuptools in the virtual environment. - :param context: The information for the environment creation request - being processed. + :param context: The information for the virtual environment + creation request being processed. """ url = 'https://bitbucket.org/pypa/setuptools/downloads/ez_setup.py' self.install_script(context, 'setuptools', url) @@ -348,10 +362,10 @@ subclass which installs setuptools and pip into a created venv:: def install_pip(self, context): """ - Install pip in the environment. + Install pip in the virtual environment. - :param context: The information for the environment creation request - being processed. + :param context: The information for the virtual environment + creation request being processed. """ url = 'https://raw.github.com/pypa/pip/master/contrib/get-pip.py' self.install_script(context, 'pip', url) @@ -374,7 +388,8 @@ subclass which installs setuptools and pip into a created venv:: 'more target ' 'directories.') parser.add_argument('dirs', metavar='ENV_DIR', nargs='+', - help='A directory to create the environment in.') + help='A directory in which to create the + 'virtual environment.') parser.add_argument('--no-setuptools', default=False, action='store_true', dest='nodist', help="Don't install setuptools or pip in the " @@ -398,14 +413,17 @@ subclass which installs setuptools and pip into a created venv:: 'the platform.') parser.add_argument('--clear', default=False, action='store_true', dest='clear', help='Delete the contents of the ' - 'environment directory if it ' - 'already exists, before ' + 'virtual environment ' + 'directory if it already ' + 'exists, before virtual ' 'environment creation.') parser.add_argument('--upgrade', default=False, action='store_true', - dest='upgrade', help='Upgrade the environment ' - 'directory to use this version ' - 'of Python, assuming Python ' - 'has been upgraded in-place.') + dest='upgrade', help='Upgrade the virtual ' + 'environment directory to ' + 'use this version of ' + 'Python, assuming Python ' + 'has been upgraded ' + 'in-place.') parser.add_argument('--verbose', default=False, action='store_true', dest='verbose', help='Display the output ' 'from the scripts which ' |