README_STYLE.md

Qiskit Metal Style Guide

The Metal code style sticks to the PEP-8 convention for Python code.

PEP-8 Cheat Sheet

Naming Conventions

• Never use I, O, or l single letter names as these can be mistaken for 1 and 0 depending on typeface.
• Use snake case for function names. e.g. function, my_function
• Use snake case for method names. e.g. class_method, method
• Use snake case for variable names. e.g. x, var, my_variable
• Use snake case for module names. e.g. module.py, my_modeul.py
• Use camel case for class names. e.g. Model, MyClass
• Use all capital letters for constants. e.g. CONSTANT, MY_CONSTANT

Maximum Line Length

• Line length should be limited to 79 characters.
• Python will assume line continuation if the code is contained within parentheses, brackets, or braces:

def function(arg_one, arg_two,
             arg_three, arg_four):
    return arg_one

• Use a backslash to break lines that a too long:

from mypackage import example1, example2 \
    example3

Indentation

• Use 4 spaces to indicate indentation.
• Spaces are preferred over tabs

Comments

• Use complete sentences, starting with a capital letter.
• Remember to update the comments when the code changes.
• Indent block comments to the same level as the code they describe.
• Start each line with a # followed by a single space.
• Separate paragraphs by a line containing a single #.
• Use inline comments sparingly.
• Don't use inline comments to explain the obvious.

When to Avoid Adding Whitespace

• At the end of a line.
• Immediately inside parentheses, brackets, or braces.
• Before a comma, semicolon, or colon.
• Before the open parenthesis that starts the argument list of a function.
• Before the open bracket that starts an index.
• Between a trailing comma and a closing parenthesis.

Where to Put Closing Braces

• Line up the closing brace with the first character of the line that starts the construct:

list_of_numbers = [
    1, 2, 3,
    4, 5, 6
]

Whitespace Around Binary Operators

• Surround assignment and comparison binary operators with a single space on either side.
• When = is used to assign a default value to a function argument do not surround it with spaces.

Other Recommendations

• To be sure a function can't be called again, use the del method.

my_function()
del my_function

• Use a function when you want to do something.
• Use a class to define a specific thing that does something.
• Define simple interfaces over simple implementation.
• Utilize encapsulation and abstraction to manage complexity.
• Define errors out of existence

PEP-8 Style Guide

For a more complete understanding of PEP-8, familiarize yourself with the complete Python Style Guide.