circuitpython/CODECONVENTIONS.md

Python code conventions

Python code follows PEP 8.

Naming conventions:

• Module names are short and all lowercase; eg pyb, stm.
• Class names are CamelCase, with abreviations all uppercase; eg I2C, not I2c.
• Function and method names are all lowercase with words separated by a single underscore as necessary to improve readability; eg mem_read.
• Constants are all uppercase with words separated by a single underscore; eg GPIO_IDR.

C code conventions

When writing new C code, please adhere to the following conventions.

White space:

• Expand tabs to 4 spaces.
• Don't leave trailing whitespace at the end of a line.
• For control blocks (if, for, while), put 1 space between the keyword and the opening parenthesis.
• Put 1 space after a comma, and 1 space around operators.

Braces:

• Use braces for all blocks, even no-line and single-line pieces of code.
• Put opening braces on the end of the line it belongs to, not on a new line.
• For else-statements, put the else on the same line as the previous closing brace.

Header files:

• Try to stick to the Plan 9 header style, where header files do not include other header files.
• Don't protect a header file from multiple inclusion with #if directives.

Type names and declarations:

• When defining a type, put '_t' after it.

Integer types: Micro Python runs on 32 and 64 bit machines (and one day maybe 16 bit), so it's important to use the correctly-sized (and signed) integer types. The general guidelines are:

• For most cases use mp_int_t for signed and mp_uint_t for unsigned integer values. These are guaranteed to be machine-word sized and therefore big enough to hold the value from a Micro Python small-int object.
• Use size_t for things that count bytes / sizes of objects.
• You can use int/uint, but remember that they may be 16-bits wide.
• If in doubt, use mp_int_t/mp_uint_t.

Examples

Braces and spaces:

int foo(int x, int y) {
    if (x < y) {
        foo(y, x);
    } else {
        foo(x + 1, y - 1);
    }

    for (int i = 0; i < x; i++) {
    }
}

Type declarations:

typedef struct _my_struct_t {
    int member;
    void *data;
} my_struct_t;