The following convention should be followed for variable naming:
snake_case or descriptive word all in lowercase for any type of variables except CONSTANTS.
ALL_CAPS for constants. python doesnot have the concept of constants so this is just a convention.
Variable Privacy is not something that python encourages or supports but there may be case where privacy is required.
__{variable_name} if you want something to denote private.
_{variable_name} if you want something to denote not publicly used or something that may change later.
__{variable_name} are not directly accesible while _{variable_name} are. They are just for convention.
Avoid builtin variable clash. Especially in globals. You can attach _ as suffix to builtin names if you deem the name necessary for your variable.
all or id is very tempting variable names but they are builtin methods in python. Go with all_ or id_ for these or better yet choose something else as a name.
While it is tempting to use i, k, v and f especially in contexts and for loops. Please avoid them.
use key, value, index instead.
use descriptive contexts such as with open(FILENAME) as open_file: pass rather than with open(FILENAME) as f: pass