Issue 3950 - Extend the Python coding practices

pages/coding-style.html

 title=Coding Style
 
 
 <h2 id="precedence">{{s1 Precedence}}</h2>
 
 <p>{{s2 The Adblock Plus coding style is based on others. Our rules (both general and language specific) always overrule referenced style guides. The language specific sections overrule the general section.}}</p>
 
 <h2 id="consistency">{{s3 Consistency}}</h2>
 
 <p>{{s4 Consistency is most important: Be consistent within functions, files, modules and projects. Making existing code conform with this style guide is fine, but it should happen in dedicated commits, preferably for a whole module or project at once.}}</p>
 
 <h2 id="general">{{s5 General}}</h2>
 <ul>
   <li>{{s6 Follow the Mozilla Coding Style's <a href="https://developer.mozilla.org/en-US/docs/Developer_Guide/Coding_Style#General_C.2FC.2B.2B_Practices">general practices</a> and its <a href="https://developer.mozilla.org/en-US/docs/Developer_Guide/Coding_Style#Naming_and_Formatting_code">naming and formatting rules</a>.}}</li>
-  <li>{{s7 Use 2 spaces per indentation level.}}</li>
   <li>{{s8 All files should have a <a href="license-headers">license header</a>, but no mode line comments.}}</li>
   <li>{{s9 Newline at end of file, otherwise no trailing whitespace.}}</li>
   <li>{{s10 Lines can be longer than the limit, if limiting line length would hurt readability in a particular case.}}</li>
   <li>{{s11 Opening braces always go on their own line.}}</li>
   <li>{{s12 No hungarian notation, no special variable name prefixes or suffixes denoting type or scope. All variable names start with a lower case letter.}}</li>
   <li>{{s13 Don't comment code out, delete it.}}</li>
   <li>{{todo-comments Don't add TODO comments, create an <a href="https://issues.adblockplus.org">issue</a> and reference it in a comment instead.}}</li>
 </ul>
 
 <h2 id="javascript">{{s14 JavaScript}}</h2>
@@ skipping 11 matching lines @@
   <li>{{html-css-optional-tag Don't omit optional HTML tags.}}</li>
   <li>{{html-css-hexadecimal CSS color values should be specified in hexadecimal where possible.}}</li>
   <li>{{html-css-shorthand CSS shorthand properties usage is optional.}}</li>
   <li>{{html-css-order CSS rule declaration order should follow the <a href="https://make.wordpress.org/core/handbook/best-practices/coding-standards/css/#property-ordering">WordPress CSS Coding Standards</a>.}}</li>
   <li>{{html-css-units CSS number values should specify units where possible.}}</li>
   <li>{{html-css-leading-zero Don't omit the optional leading 0 for decimal numbers.}}</li>
 </ul>
 
 <h2 id="python">{{s19 Python}}</h2>
 <ul>
-  <li>{{s20 Follow the Mozilla Coding Style's <a href="https://developer.mozilla.org/en-US/docs/Developer_Guide/Coding_Style#Python_Practices">Python practices</a>.}}</li>
-  <li>{{s21 In modules, prefix private functions and variables with a single underscore.}}</li>
+  <li>{{python-general Follow <a href="https://www.python.org/dev/peps/pep-0008/">PEP-8</a> and the Mozilla Coding Style's <a href="https://developer.mozilla.org/en-US/docs/Developer_Guide/Coding_Style#Python_Practices">Python practices</a>.}}</li>
+  <li>{{python-prefix In modules, prefix private functions and variables with a single underscore.}}</li>
+  <li>{{python-concatenation Use the <code><fix>+</fix></code> operator when concatenating exactly two strings, use the <a href="https://docs.python.org/2/library/stdtypes.html#str.format"><code><fix>format()</fix></code> method</a> for more complex string formatting, use the <a href="https://docs.python.org/2/library/stdtypes.html#str.join"><code><fix>join()</fix></code> method</a> when concatenating pre-existing sequences.}}</li>
+  <li>{{python-tuple-vs-list Use tuples for data that have structure, use lists for data that have order.}}</li>
 </ul>
 
 <h2 id="java">{{s22 Java}}</h2>
 <ul>
   <li>{{s23 Follow the Mozilla Coding Style's <a href="https://developer.mozilla.org/en-US/docs/Developer_Guide/Coding_Style#Java_practices">Java practices</a>.}}</li>
   <li>{{s24 Imports should be organised consistently per file, we don't use global rules.}}</li>
 </ul>
 
 <h2 id="cpp">{{s25 C++}}</h2>
 <ul>
   <li>{{s26 Follow the Mozilla Coding Style's <a href="https://developer.mozilla.org/en-US/docs/Developer_Guide/Coding_Style#C.2FC.2B.2B_practices">C++ practices</a>.}}</li>
   <li>{{s27 Indent namespace bodies.}}</li>
   <li>{{s28 Avoid manual memory management: Use references and values when possible, smart pointers when necessary, raw pointers only for weak references.}}</li>
   <li>{{s29 Don't use C-style casts unless its exact semantics are required.}}</li>
   <li>{{s30 We tend to use anonymous namespaces instead of static.}}</li>
 </ul>
 
 <h2 id="objc">{{objective-c Objective-C}}</h2>
 <ul>
   <li>{{objc-conventions Follow Apple's <a href="https://developer.apple.com/library/ios/documentation/Cocoa/Conceptual/ProgrammingWithObjectiveC/Conventions/Conventions.html">conventions</a>}}.</li>
 </ul>
 
 <h2 id="puppet">{{s31 Puppet}}</h2>
 <ul>
   <li>{{s32 Follow the <a href="http://docs.puppetlabs.com/guides/style_guide.html">Puppet Style Guide</a>.}}</li>
   <li>{{s33 Opening braces don't go on their own line.}}</li>
   <li>{{s34 Arrows should not be aligned.}}</li>
 </ul>