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This means it may not be possible for one Python installation vikings season 4 episode 15 meet the requirements of every application. If application A needs version 1. The solution for this problem is to create a virtual environmenta self-contained directory tree that contains a Python installation for a particular version of Python, plus a number of additional packages. Different applications can then use different virtual environments.
To resolve the earlier example of conflicting requirements, application A can have its own virtual environment with version 1. If application B requires a library be upgraded to version 3. The module used to create and manage virtual environments is called venv. If you have multiple versions of Python on your system, you can select a specific Python version by running python3 or whichever version you want. To create a virtual environment, decide upon a directory where you want to place it, and run the venv module as a script with the directory path:.
A common directory location for a virtual environment is. This name keeps the directory typically hidden in your shell and thus out of the way while giving it a name that explains why the directory exists. It also prevents clashing with. This script is written for the bash shell.
If you use the csh or birth chart compatibility with your partner shells, there are alternate activate.
For example:. You can install, upgrade, and remove packages using a program called pip. Consult the Installing Python Modules guide for complete documentation for pip.
If you re-run this command, pip will notice that the requested version is already installed and do nothing.
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You can supply a different version number to get that version, or you can run pip install --upgrade to upgrade the package to the latest version:. A common convention is to put this list in a requirements. The requirements. Users can then install all the necessary packages with install -r :. What Now? To create a virtual environment, decide upon a directory where you want to place it, and run the venv module as a script with the directory path: python3 - m venv tutorial - env.
Note: Python 3. Full Changelog. Skip to content. Release Date: Dec. Python 3. Major new features of the 3. More resources Online Documentation 3. Help fund Python and its community. Notes on this release The binaries for AMD64 will also work on processors that implement the Intel 64 architecture. Also known as the "x64" architecture, and formerly known as both "EM64T" and "x".
Windows users: If installing Python 3. Windows users: There are now "web-based" installers for Windows platforms; the installer will download the needed software components at installation time. Windows Users: There are redistributable zip files containing the Windows builds, making it easy to redistribute Python as part of another software package. Please see the documentation regarding Embedded Distribution for more information. XZ compressed source tarball.
Windows x embeddable zip file. Windows x executable installer. Windows x web-based installer.Python Module Index Python 3. The Python Software Foundation is a non-profit corporation. Please donate. Last updated on Dec 06, Found a bug? Created using Sphinx 1. Homepage Table of contents 3. Data Instead Of Unicode Vs.
Core and Builtins Windows Python 3. Build Python 3. Library Build Python 3. Core and Builtins Library Python 3. Core and Builtins Library Build Python 3. Library Documentation Python 3. TCPServer Example socketserver. Widget Combobox Options Virtual events ttk. Notebook Progressbar Options ttk. Treeview Ttk Styling Layouts tkinter. How are Docstring Examples Recognized? What's the Execution Context? What About Exceptions? What are positional arguments for?What's new in Python 3.
Tutorial start here. Library Reference keep this under your pillow. Language Reference describes syntax and language elements. Python Setup and Usage how to use Python on different platforms. Distributing Python Modules publishing modules for installation by others. FAQs frequently asked questions with answers!
Global Module Index quick access to all modules. General Index all functions, classes, terms. Glossary the most important terms explained. Search page search this documentation. Complete Table of Contents lists all sections and subsections. Contributing to Docs. Python 3. This is the documentation for Python 3.
Parts of the documentation: What's new in Python 3. Indices and tables: Global Module Index quick access to all modules General Index all functions, classes, terms Glossary the most important terms explained Search page search this documentation Complete Table of Contents lists all sections and subsections Meta information: Reporting bugs Contributing to Docs About the documentation History and License of Python Copyright.
Download Download these documents Docs by version Python 3. The Python Software Foundation is a non-profit corporation. Please donate. Last updated on Oct 11, Found a bug? Created using Sphinx 2. Global Module Index quick access to all modules General Index all functions, classes, terms Glossary the most important terms explained.
Search page search this documentation Complete Table of Contents lists all sections and subsections.Released: Oct 6, View statistics for this project via Libraries. Author: Manfred Stienstra, Yuri takhteyev and Waylan limberg. This is a Python implementation of John Gruber's Markdown. It is almost completely compliant with the reference implementation, though there are a few known issues. See Features for information on what exactly is supported and what is not.
Additional features are supported by the Available Extensions. You may report bugs, ask for help, and discuss various other issues on the bug tracker. Everyone interacting in the Python-Markdown project's codebases, issue trackers, and mailing lists is expected to follow the Code of Conduct. Oct 6, May 8, Feb 12, Feb 7, May 21, Mar 26, Sep 26, Sep 22, Jan 5, Dec 8, Aug 18, Jan 25, Sep 24, Mar 21, Nov 25, Nov 6, Oct 26, Apr 20, Mar 9, Feb 20, Nov 20, Sep 13, May 22, Feb 16, Mar 22, Mar 15, Nov 4, Jul 5, Jan 22, Nov 24, Python is an interpretedhigh-level and general-purpose programming language.
Created by Guido van Rossum and first released inPython's design philosophy emphasizes code readability with its notable use of significant whitespace.
Browse the docs online or download a copy of your own.
Its language constructs and object-oriented approach aim to help programmers write clear, logical code for small and large-scale projects.
Python is dynamically typed and garbage-collected. It supports multiple programming paradigmsincluding structured particularly, proceduralobject-orientedand functional programming. Python is often described as a "batteries included" language due to its comprehensive standard library. Python was created in the late s as a successor to the ABC language. Python interpreters are available for many operating systems.
A global community of programmers develops and maintains CPythona free and open-source  reference implementation. A non-profit organization, the Python Software Foundationmanages and directs resources for Python and CPython development.
Python 2. Python 3. It was a major revision of the language that is not completely backward-compatible. Releases of Python 3 include the 2to3 utility, which automates at least partially the translation of Python 2 code to Python 3. Python is a multi-paradigm programming language. Object-oriented programming and structured programming are fully supported, and many of its features support functional programming and aspect-oriented programming including by metaprogramming  and metaobjects magic methods.
Python uses dynamic typing and a combination of reference counting and a cycle-detecting garbage collector for memory management. Python's design offers some support for functional programming in the Lisp tradition. It has filtermapand reduce functions; list comprehensionsdictionariessets, and generator expressions. The language's core philosophy is summarized in the document The Zen of Python PEP 20which includes aphorisms such as: . Rather than having all of its functionality built into its core, Python was designed to be highly extensible.
This compact modularity has made it particularly popular as a means of adding programmable interfaces to existing applications. Van Rossum's vision of a small core language with a large standard library and easily extensible interpreter stemmed from his frustrations with ABCwhich espoused the opposite approach. Python strives for a simpler, less-cluttered syntax and grammar while giving developers a choice in their coding methodology.
In contrast to Perl 's " there is more than one way to do it " motto, Python embraces a "there should be one—and preferably only one—obvious way to do it" design philosophy. Python's developers strive to avoid premature optimizationand reject patches to non-critical parts of the CPython reference implementation that would offer marginal increases in speed at the cost of clarity. An important goal of Python's developers is keeping it fun to use.
This is reflected in the language's name—a tribute to the British comedy group Monty Python  —and in occasionally playful approaches to tutorials and reference materials, such as examples that refer to spam and eggs from a famous Monty Python sketch instead of the standard foo and bar.
A common neologism in the Python community is pythonicwhich can have a wide range of meanings related to program style. To say that code is pythonic is to say that it uses Python idioms well, that it is natural or shows fluency in the language, that it conforms with Python's minimalist philosophy and emphasis on readability. In contrast, code that is difficult to understand or reads like a rough transcription from another programming language is called unpythonic.
Users and admirers of Python, especially those considered knowledgeable or experienced, are often referred to as Pythonistas. Python is meant to be an easily readable language. Its formatting is visually uncluttered, and it often uses English keywords where other languages use punctuation. Unlike many other languages, it does not use curly brackets to delimit blocks, and semicolons after statements are optional. It has fewer syntactic exceptions and special cases than C or Pascal.
Python uses whitespace indentation, rather than curly brackets or keywords, to delimit blocks. An increase in indentation comes after certain statements; a decrease in indentation signifies the end of the current block. Python's statements include among others :.Add an item to the end of the list.
Extend the list by appending all the items from the iterable. Insert an item at a given position. The first argument is the index of the element before which to insert, so a. Remove the first item from the list whose value is equal to x. It raises a ValueError if there is no such item. Remove the item at the given position in the list, and return it.
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If no index is specified, a. The square brackets around the i in the method signature denote that the parameter is optional, not that you should type square brackets at that position.
You will see this notation frequently in the Python Library Reference. Remove all items from the list. Equivalent to del a[:]. Return zero-based index in the list of the first item whose value is equal to x. Raises a ValueError if there is no such item.
The optional arguments start and end are interpreted as in the slice notation and are used to limit the search to a particular subsequence of the list.
The returned index is computed relative to the beginning of the full sequence rather than the start argument. Sort the items of the list in place the arguments can be used for sort customization, see sorted for their explanation. Return a shallow copy of the list. Equivalent to a[:]. You might have noticed that methods like insertremove or sort that only modify the list have no return value printed — they return the default None.
Another thing you might notice is that not all data can be sorted or compared. To add an item to the top of the stack, use append. To retrieve an item from the top of the stack, use pop without an explicit index. For example:. While appends and pops from the end of list are fast, doing inserts or pops from the beginning of a list is slow because all of the other elements have to be shifted by one. To implement a queue, use collections. List comprehensions provide a concise way to create lists.
Common applications are to make new lists where each element is the result of some operations applied to each member of another sequence or iterable, or to create a subsequence of those elements that satisfy a certain condition.
Note that this creates or overwrites a variable named x that still exists after the loop completes. We can calculate the list of squares without any side effects using:. A list comprehension consists of brackets containing an expression followed by a for clause, then zero or more for or if clauses. The result will be a new list resulting from evaluating the expression in the context of the for and if clauses which follow it.
For example, this listcomp combines the elements of two lists if they are not equal:. Note how the order of the for and if statements is the same in both these snippets. If the expression is a tuple e. The initial expression in a list comprehension can be any arbitrary expression, including another list comprehension.
As we saw in the previous section, the nested listcomp is evaluated in the context of the for that follows it, so this example is equivalent to:. In the real world, you should prefer built-in functions to complex flow statements.