diff --git a/docs/index.rst b/docs/index.rst index dcd56579f..df7fcb8ed 100644 --- a/docs/index.rst +++ b/docs/index.rst @@ -4,7 +4,7 @@ contain the root `toctree` directive. .. meta:: - :description: An opinionated guide to the Python programming language and a best practice handbook to the installation, configuration, and usage of Python on a daily basis. + :description: An opinionated guide to the Python programming language and a best practice handbook for the installation, configuration, and usage of Python on a daily basis. ################################# @@ -17,7 +17,7 @@ Greetings, Earthling! Welcome to The Hitchhiker's Guide to Python. `fork us on GitHub `_! This handcrafted guide exists to provide both novice and expert Python -developers a best practice handbook to the installation, configuration, and +developers a best practice handbook for the installation, configuration, and usage of Python on a daily basis. This guide is **opinionated** in a way that is almost, but not quite, entirely @@ -25,7 +25,7 @@ This guide is **opinionated** in a way that is almost, but not quite, entirely available here. Rather, you'll find a nice concise list of highly recommended options. -.. note:: The use of **Python 3** is *highly* preferred over Python 2. Consider upgrading your applications and infrastructure if you find yourself *still* using Python 2 in production today. If you are using Python 3, congratulations — you are indeed a person of excellent taste. +.. note:: The use of **Python 3** is *highly* recommended over Python 2. Consider upgrading your applications and infrastructures if you find yourself *still* using Python 2 in production today. If you are using Python 3, congratulations — you are indeed a person of excellent taste. —*Kenneth Reitz* Let's get started! But first, let's make sure you know where your towel is. diff --git a/docs/scenarios/admin.rst b/docs/scenarios/admin.rst index 826906af0..07d263945 100644 --- a/docs/scenarios/admin.rst +++ b/docs/scenarios/admin.rst @@ -199,7 +199,7 @@ Ansible ******* `Ansible `_ is an open source system automation tool. -The biggest advantage over Puppet or Chef is it does not require an agent on +Its biggest advantage over Puppet or Chef is that it does not require an agent on the client machine. Playbooks are Ansible’s configuration, deployment, and orchestration language and are written in YAML with Jinja2 for templating. diff --git a/docs/scenarios/ci.rst b/docs/scenarios/ci.rst index ade9148c4..4296679c7 100644 --- a/docs/scenarios/ci.rst +++ b/docs/scenarios/ci.rst @@ -65,7 +65,7 @@ Travis-CI tests for open source projects for free. It provides multiple workers to run Python tests on and seamlessly integrates with GitHub. You can even have it comment on your Pull Requests whether this particular changeset breaks the -build or not. So if you are hosting your code on GitHub, Travis-CI is a great +build or not. So, if you are hosting your code on GitHub, Travis-CI is a great and easy way to get started with Continuous Integration. In order to get started, add a :file:`.travis.yml` file to your repository with diff --git a/docs/starting/which-python.rst b/docs/starting/which-python.rst index b1e3a8212..59d42352e 100644 --- a/docs/starting/which-python.rst +++ b/docs/starting/which-python.rst @@ -31,7 +31,7 @@ Recommendations *************** -.. note:: The use of **Python 3** is *highly* preferred over Python 2. Consider upgrading your applications and infrastructure if you find yourself *still* using Python 2 in production today. If you are using Python 3, congratulations — you are indeed a person of excellent taste. +.. note:: The use of **Python 3** is *highly* recommended over Python 2. Consider upgrading your applications and infrastructure if you find yourself *still* using Python 2 in production today. If you are using Python 3, congratulations — you are indeed a person of excellent taste. —*Kenneth Reitz* I'll be blunt: diff --git a/docs/writing/documentation.rst b/docs/writing/documentation.rst index 4d72a544d..27d85405a 100644 --- a/docs/writing/documentation.rst +++ b/docs/writing/documentation.rst @@ -45,7 +45,7 @@ Project Publication Depending on the project, your documentation might include some or all of the following components: -- An *introduction* should show a very short overview of what can be +- An *introduction* should give a very short overview of what can be done with the product, using one or two extremely simplified use cases. This is the thirty-second pitch for your project. @@ -94,7 +94,7 @@ reStructuredText ~~~~~~~~~~~~~~~~ Most Python documentation is written with reStructuredText_. It's like -Markdown with all the optional extensions built in. +Markdown, but with all the optional extensions built in. The `reStructuredText Primer`_ and the `reStructuredText Quick Reference`_ should help you familiarize yourself with its syntax. @@ -149,8 +149,8 @@ a project's documentation. Additionally, Doctest_ will read all embedded docstrings that look like input from the Python commandline (prefixed with ">>>") and run them, checking to see if the output of the command matches the text on the following line. This -allows developers to embed real examples and usage of functions alongside -their source code, and as a side effect, it also ensures that their code is +allows developers to embed real examples and usage of functions alongside +their source code. As a side effect, it also ensures that their code is tested and works. :: @@ -187,8 +187,8 @@ Docstrings are accessible from both the `__doc__` dunder attribute for almost every Python object, as well as with the built in `help()` function. While block comments are usually used to explain *what* a section of code is -doing, or the specifics of an algorithm, docstrings are more intended for -explaining to other users of your code (or you in 6 months time) *how* a +doing, or the specifics of an algorithm, docstrings are more intended towards +explaining other users of your code (or you in 6 months time) *how* a particular function can be used and the general purpose of a function, class, or module. @@ -214,7 +214,7 @@ In larger or more complex projects however, it is often a good idea to give more information about a function, what it does, any exceptions it may raise, what it returns, or relevant details about the parameters. -For more detailed documentation of code a popular style is the one used for the +For more detailed documentation of code a popular style used, is the one used by the NumPy project, often called `NumPy style`_ docstrings. While it can take up more lines than the previous example, it allows the developer to include a lot more information about a method, function, or class. :: diff --git a/docs/writing/gotchas.rst b/docs/writing/gotchas.rst index 677bdf823..f717858ca 100644 --- a/docs/writing/gotchas.rst +++ b/docs/writing/gotchas.rst @@ -7,13 +7,13 @@ Common Gotchas .. image:: /_static/photos/34435688380_b5a740762b_k_d.jpg For the most part, Python aims to be a clean and consistent language that -avoids surprises. However, there are a few cases that can be confusing to +avoids surprises. However, there are a few cases that can be confusing for newcomers. Some of these cases are intentional but can be potentially surprising. Some could arguably be considered language warts. In general, what follows is a collection of potentially tricky behavior that might seem strange at first -glance, but is generally sensible once you're aware of the underlying cause for +glance, but are generally sensible, once you're aware of the underlying cause for the surprise. @@ -53,8 +53,8 @@ isn't provided, so that the output is:: [12] [42] -What Does Happen -~~~~~~~~~~~~~~~~ +What Actually Happens +~~~~~~~~~~~~~~~~~~~~~ .. testoutput:: @@ -100,6 +100,7 @@ Late Binding Closures Another common source of confusion is the way Python binds its variables in closures (or in the surrounding global scope). + What You Wrote ~~~~~~~~~~~~~~ @@ -125,8 +126,8 @@ variable that multiplies their argument, producing:: 6 8 -What Does Happen -~~~~~~~~~~~~~~~~ +What Actually Happens +~~~~~~~~~~~~~~~~~~~~~ .. testoutput:: @@ -206,7 +207,7 @@ will automatically write a bytecode version of that file to disk, e.g. These ``.pyc`` files should not be checked into your source code repositories. Theoretically, this behavior is on by default for performance reasons. -Without these bytecode files present, Python would re-generate the bytecode +Without these bytecode files, Python would re-generate the bytecode every time the file is loaded. diff --git a/docs/writing/license.rst b/docs/writing/license.rst index 0a74f5405..820cc9a05 100644 --- a/docs/writing/license.rst +++ b/docs/writing/license.rst @@ -6,8 +6,8 @@ Choosing a License .. image:: /_static/photos/33907149294_82d7535a6c_k_d.jpg -Your source publication *needs* a license. In the US, if no license is -specified, users have no legal right to download, modify, or distribute. +Your source publication *needs* a license. In the US, unless a license is +specified, users have no legal right to download, modify, or distribute the product. Furthermore, people can't contribute to your code unless you tell them what rules to play by. Choosing a license is complicated, so here are some pointers: diff --git a/docs/writing/logging.rst b/docs/writing/logging.rst index b609dc721..b6110f7f7 100644 --- a/docs/writing/logging.rst +++ b/docs/writing/logging.rst @@ -10,7 +10,7 @@ The :mod:`logging` module has been a part of Python's Standard Library since version 2.3. It is succinctly described in :pep:`282`. The documentation is notoriously hard to read, except for the `basic logging tutorial`_. -As an alternative, `loguru `_ provides an approach to logging nearly as simple as using a simple ``print`` statement. +As an alternative, `loguru `_ provides an approach for logging, nearly as simple as using a simple ``print`` statement. Logging serves two purposes: @@ -59,7 +59,7 @@ using the ``__name__`` global variable: the :mod:`logging` module creates a hierarchy of loggers using dot notation, so using ``__name__`` ensures no name collisions. -Here is an example of best practice from the `requests source`_ -- place +Here is an example of the best practice from the `requests source`_ -- place this in your ``__init__.py``: .. code-block:: python @@ -83,7 +83,7 @@ application environment. There are at least three ways to configure a logger: - Using an INI-formatted file: - - **Pro**: possible to update configuration while running using the + - **Pro**: possible to update configuration while running, using the function :func:`logging.config.listen` to listen on a socket. - **Con**: less control (e.g. custom subclassed filters or loggers) than possible when configuring a logger in code. @@ -94,13 +94,13 @@ There are at least three ways to configure a logger: - **Con**: less control than when configuring a logger in code. - Using code: - **Pro**: complete control over the configuration. - - **Con**: modifications require a change to source code. + - **Con**: modifications require a change to the source code. Example Configuration via an INI File ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -Let us say the file is named ``logging_config.ini``. +Let us say that the file is named ``logging_config.ini``. More details for the file format are in the `logging configuration`_ section of the `logging tutorial`_. diff --git a/docs/writing/structure.rst b/docs/writing/structure.rst index bbbef47fe..b8da9decd 100644 --- a/docs/writing/structure.rst +++ b/docs/writing/structure.rst @@ -18,7 +18,7 @@ the project? What features and functions can be grouped together and isolated? By answering questions like these you can begin to plan, in a broad sense, what your finished product will look like. -In this section we take a closer look at Python's module and import +In this section, we take a closer look at Python's modules and import systems as they are the central elements to enforcing structure in your project. We then discuss various perspectives on how to build code which can be extended and tested reliably. @@ -32,7 +32,7 @@ It's Important. ::::::::::::::: Just as Code Style, API Design, and Automation are essential for a -healthy development cycle, Repository structure is a crucial part of +healthy development cycle. Repository structure is a crucial part of your project's `architecture `__. @@ -54,8 +54,7 @@ documentation. Of course, first impressions aren't everything. You and your colleagues will spend countless hours working with this repository, eventually -becoming intimately familiar with every nook and cranny. The layout of -it is important. +becoming intimately familiar with every nook and cranny. The layout is important. Sample Repository ::::::::::::::::: @@ -126,7 +125,7 @@ If you aren't sure which license you should use for your project, check out `choosealicense.com `_. Of course, you are also free to publish code without a license, but this -would prevent many people from potentially using your code. +would prevent many people from potentially using or contributing to your code. Setup.py :::::::: @@ -157,8 +156,8 @@ should be placed at the root of the repository. It should specify the dependencies required to contribute to the project: testing, building, and generating documentation. -If your project has no development dependencies, or you prefer -development environment setup via ``setup.py``, this file may be +If your project has no development dependencies, or if you prefer +setting up a development environment via ``setup.py``, this file may be unnecessary. Documentation @@ -331,42 +330,42 @@ Easy structuring of a project means it is also easy to do it poorly. Some signs of a poorly structured project include: -- Multiple and messy circular dependencies: if your classes +- Multiple and messy circular dependencies: If the classes Table and Chair in :file:`furn.py` need to import Carpenter from :file:`workers.py` to answer a question such as ``table.isdoneby()``, and if conversely the class Carpenter needs to import Table and Chair to answer the question ``carpenter.whatdo()``, then you have a circular dependency. In this case you will have to resort to - fragile hacks such as using import statements inside + fragile hacks such as using import statements inside your methods or functions. -- Hidden coupling: each and every change in Table's implementation +- Hidden coupling: Each and every change in Table's implementation breaks 20 tests in unrelated test cases because it breaks Carpenter's code, - which requires very careful surgery to adapt the change. This means + which requires very careful surgery to adapt to the change. This means you have too many assumptions about Table in Carpenter's code or the reverse. -- Heavy usage of global state or context: instead of explicitly +- Heavy usage of global state or context: Instead of explicitly passing ``(height, width, type, wood)`` to each other, Table and Carpenter rely on global variables that can be modified and are modified on the fly by different agents. You need to - scrutinize all access to these global variables to understand why + scrutinize all access to these global variables in order to understand why a rectangular table became a square, and discover that remote template code is also modifying this context, messing with - table dimensions. + the table dimensions. - Spaghetti code: multiple pages of nested if clauses and for loops with a lot of copy-pasted procedural code and no proper segmentation are known as spaghetti code. Python's - meaningful indentation (one of its most controversial features) make - it very hard to maintain this kind of code. So the good news is that + meaningful indentation (one of its most controversial features) makes + it very hard to maintain this kind of code. The good news is that you might not see too much of it. - Ravioli code is more likely in Python: it consists of hundreds of similar little pieces of logic, often classes or objects, without - proper structure. If you never can remember if you have to use + proper structure. If you never can remember, if you have to use FurnitureTable, AssetTable or Table, or even TableNew for your - task at hand, you might be swimming in ravioli code. + task at hand, then you might be swimming in ravioli code. ******* @@ -384,13 +383,13 @@ in one file, and all low-level operations in another file. In this case, the interface file needs to import the low-level file. This is done with the ``import`` and ``from ... import`` statements. -As soon as you use `import` statements you use modules. These can be either +As soon as you use `import` statements, you use modules. These can be either built-in modules such as `os` and `sys`, third-party modules you have installed in your environment, or your project's internal modules. To keep in line with the style guide, keep module names short, lowercase, and be sure to avoid using special symbols like the dot (.) or question mark (?). -So a file name like :file:`my.spam.py` is one you should avoid! Naming this way +A file name like :file:`my.spam.py` is the one you should avoid! Naming this way will interfere with the way Python looks for modules. In the case of `my.spam.py` Python expects to find a :file:`spam.py` file in a @@ -398,10 +397,10 @@ folder named :file:`my` which is not the case. There is an `example `_ of how the dot notation should be used in the Python docs. -If you'd like you could name your module :file:`my_spam.py`, but even our -friend the underscore should not be seen often in module names. However, using other +If you like, you could name your module :file:`my_spam.py`, but even our trusty +friend the underscore, should not be seen that often in module names. However, using other characters (spaces or hyphens) in module names will prevent importing -(- is the subtract operator), so try to keep module names short so there is +(- is the subtract operator). Try to keep module names short so there is no need to separate words. And, most of all, don't namespace with underscores; use submodules instead. .. code-block:: python @@ -412,15 +411,15 @@ no need to separate words. And, most of all, don't namespace with underscores; u import library.foo_plugin Aside from some naming restrictions, nothing special is required for a Python -file to be a module, but you need to understand the import mechanism in order +file to be a module. But you need to understand the import mechanism in order to use this concept properly and avoid some issues. Concretely, the ``import modu`` statement will look for the proper file, which -is :file:`modu.py` in the same directory as the caller if it exists. If it is +is :file:`modu.py` in the same directory as the caller, if it exists. If it is not found, the Python interpreter will search for :file:`modu.py` in the "path" -recursively and raise an ImportError exception if it is not found. +recursively and raise an ImportError exception when it is not found. -Once :file:`modu.py` is found, the Python interpreter will execute the module in +When :file:`modu.py` is found, the Python interpreter will execute the module in an isolated scope. Any top-level statement in :file:`modu.py` will be executed, including other imports if any. Function and class definitions are stored in the module's dictionary. @@ -437,7 +436,7 @@ unwanted effects, e.g. override an existing function with the same name. It is possible to simulate the more standard behavior by using a special syntax of the import statement: ``from modu import *``. This is generally considered -bad practice. **Using** ``import *`` **makes code harder to read and makes +bad practice. **Using** ``import *`` **makes the code harder to read and makes dependencies less compartmentalized**. Using ``from modu import func`` is a way to pinpoint the function you want to @@ -493,20 +492,20 @@ modules, but with a special behavior for the :file:`__init__.py` file, which is used to gather all package-wide definitions. A file :file:`modu.py` in the directory :file:`pack/` is imported with the -statement ``import pack.modu``. This statement will look for an +statement ``import pack.modu``. This statement will look for :file:`__init__.py` file in :file:`pack` and execute all of its top-level statements. Then it will look for a file named :file:`pack/modu.py` and execute all of its top-level statements. After these operations, any variable, function, or class defined in :file:`modu.py` is available in the pack.modu namespace. -A commonly seen issue is to add too much code to :file:`__init__.py` +A commonly seen issue is adding too much code to :file:`__init__.py` files. When the project complexity grows, there may be sub-packages and sub-sub-packages in a deep directory structure. In this case, importing a single item from a sub-sub-package will require executing all :file:`__init__.py` files met while traversing the tree. -Leaving an :file:`__init__.py` file empty is considered normal and even a good +Leaving an :file:`__init__.py` file empty is considered normal and even good practice, if the package's modules and sub-packages do not need to share any code. @@ -520,45 +519,44 @@ Object-oriented programming *************************** Python is sometimes described as an object-oriented programming language. This -can be somewhat misleading and needs to be clarified. +can be somewhat misleading and requires further clarifications. In Python, everything is an object, and can be handled as such. This is what is meant when we say, for example, that functions are first-class objects. Functions, classes, strings, and even types are objects in Python: like any object, they have a type, they can be passed as function arguments, and they -may have methods and properties. In this understanding, Python is an -object-oriented language. +may have methods and properties. In this understanding, Python can be considered +as an object-oriented language. However, unlike Java, Python does not impose object-oriented programming as the main programming paradigm. It is perfectly viable for a Python project to not be object-oriented, i.e. to use no or very few class definitions, class inheritance, or any other mechanisms that are specific to object-oriented -programming. +programming languages. Moreover, as seen in the modules_ section, the way Python handles modules and namespaces gives the developer a natural way to ensure the encapsulation and separation of abstraction layers, both being the most common reasons to use object-orientation. Therefore, Python programmers have more -latitude to not use object-orientation, when it is not required by the business +latitude as to not use object-orientation, when it is not required by the business model. There are some reasons to avoid unnecessary object-orientation. Defining -custom classes is useful when we want to glue together some state and some -functionality. The problem, as pointed out by the discussions about functional +custom classes is useful when we want to glue some state and some +functionality together. The problem, as pointed out by the discussions about functional programming, comes from the "state" part of the equation. In some architectures, typically web applications, multiple instances of Python -processes are spawned to respond to external requests that can happen at the -same time. In this case, holding some state in instantiated objects, which +processes are spawned as a response to external requests that happen simultaneously. +In this case, holding some state in instantiated objects, which means keeping some static information about the world, is prone to concurrency problems or race conditions. Sometimes, between the initialization of the state of an object (usually done with the ``__init__()`` method) and the actual use of the object state through one of its methods, the world may have changed, and the retained state may be outdated. For example, a request may load an item in memory and mark it as read by a user. If another request requires the deletion -of this item at the same time, it may happen that the deletion actually occurs -after the first process loaded the item, and then we have to mark as read a -deleted object. +of this item at the same time, the deletion may actually occur after the first +process loaded the item, and then we have to mark a deleted object as read. This and other issues led to the idea that using stateless functions is a better programming paradigm. @@ -572,7 +570,7 @@ or deletes data in a global variable or in the persistence layer, it is said to have a side-effect. Carefully isolating functions with context and side-effects from functions with -logic (called pure functions) allow the following benefits: +logic (called pure functions) allows the following benefits: - Pure functions are deterministic: given a fixed input, the output will always be the same. @@ -714,7 +712,7 @@ type. In fact, in Python, variables are very different from what they are in many other languages, specifically statically-typed languages. Variables are not a segment of the computer's memory where some value is written, they are 'tags' or 'names' pointing to objects. It is therefore possible for the variable 'a' to -be set to the value 1, then to the value 'a string', then to a function. +be set to the value 1, then the value 'a string', to a function. The dynamic typing of Python is often considered to be a weakness, and indeed it can lead to complexities and hard-to-debug code. Something named 'a' can be @@ -744,7 +742,7 @@ Some guidelines help to avoid this issue: def func(): pass # Do something -Using short functions or methods helps reduce the risk +Using short functions or methods helps to reduce the risk of using the same name for two unrelated things. It is better to use different names even for things that are related, @@ -846,7 +844,7 @@ most idiomatic way to do this. One final thing to mention about strings is that using ``join()`` is not always best. In the instances where you are creating a new string from a pre-determined -number of strings, using the addition operator is actually faster, but in cases +number of strings, using the addition operator is actually faster. But in cases like above or in cases where you are adding to an existing string, using ``join()`` should be your preferred method. diff --git a/docs/writing/style.rst b/docs/writing/style.rst index d40033afa..3bf029911 100644 --- a/docs/writing/style.rst +++ b/docs/writing/style.rst @@ -8,7 +8,7 @@ Code Style .. image:: /_static/photos/33907150054_5ee79e8940_k_d.jpg If you ask Python programmers what they like most about Python, they will -often cite its high readability. Indeed, a high level of readability +often cite its high readability. Indeed, a high level of readability is at the heart of the design of the Python language, following the recognized fact that code is read much more often than it is written. @@ -226,7 +226,7 @@ but making a public property private might be a much harder operation. Returning values ~~~~~~~~~~~~~~~~ -When a function grows in complexity it is not uncommon to use multiple return +When a function grows in complexity, it is not uncommon to use multiple return statements inside the function's body. However, in order to keep a clear intent and a sustainable readability level, it is preferable to avoid returning meaningful values from many output points in the body. @@ -639,12 +639,12 @@ Short Ways to Manipulate Lists `List comprehensions `_ -provide a powerful, concise way to work with lists. +provides a powerful, concise way to work with lists. `Generator expressions `_ -follow almost the same syntax as list comprehensions but return a generator -instead of a list. +follows almost the same syntax as list comprehensions but return a generator +instead of a list. Creating a new list requires more work and uses more memory. If you are just going to loop through the new list, prefer using an iterator instead. @@ -668,7 +668,7 @@ example if you need to use the result multiple times. If your logic is too complicated for a short list comprehension or generator -expression, consider using a generator function instead of returning a list. +expression, consider using a generator function instead of returning a list. **Good**: @@ -688,7 +688,7 @@ expression, consider using a generator function instead of returning a list. yield current_batch -Never use a list comprehension just for its side effects. +Never use a list comprehension just for its side effects. **Bad**: @@ -701,7 +701,7 @@ Never use a list comprehension just for its side effects. .. code-block:: python for x in sequence: - print(x) + print(x) Filtering a list @@ -728,7 +728,7 @@ Don't make multiple passes through the list. **Good**: -Use a list comprehension or generator expression. +Use a list comprehension or generator expression. .. code-block:: python @@ -829,7 +829,7 @@ a white space added to the end of the line, after the backslash, will break the code and may have unexpected results. A better solution is to use parentheses around your elements. Left with an -unclosed parenthesis on an end-of-line the Python interpreter will join the +unclosed parenthesis on an end-of-line, the Python interpreter will join the next line until the parentheses are closed. The same behavior holds for curly and square braces. diff --git a/docs/writing/tests.rst b/docs/writing/tests.rst index 7809d9ffe..28eb3260b 100644 --- a/docs/writing/tests.rst +++ b/docs/writing/tests.rst @@ -9,8 +9,8 @@ Testing Your Code Testing your code is very important. Getting used to writing testing code and running this code in parallel is now -considered a good habit. Used wisely, this method helps you define more -precisely your code's intent and have a more decoupled architecture. +considered a good habit. Used wisely, this method helps to define your +code's intent more precisely and have a more decoupled architecture. Some general rules of testing: @@ -294,6 +294,6 @@ always returns the same result (but only for the duration of the test). # get_search_results runs a search and iterates over the result self.assertEqual(len(myapp.get_search_results(q="fish")), 3) -Mock has many other ways you can configure it and control its behavior. +Mock has many other ways with which you can configure and control its behaviour. `mock `_