Naming convention in Python

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*Memo:

• My post explains an identifier.
• My post explains the single, double and triple leading and trailing underscore with the variables, methods and classes in a class.
• My post explains a variable assignment.
• My post explains a function (1).

A class name should be CapWords(PascalCase) as shown below:

class Cls: pass class MyCls: pass class MyFirstCls: pass 

A variable, function and parameter name should be lower_snake_case as shown below:

var = 'abc' my_var = 'abc' my_first_var = 'abc' 

def func(param): pass def my_func(my_param): pass def my_first_func(my_first_param): pass 

A constant name should be UPPER_SNAKE_CASE as shown below:

PI = 3.141592653589793 E = 2.718281828459045 MIN_NUM = 0 MAX_NUM = 100 MY_MIN_NUM = 0 MY_MAX_NUM = 100 

A module name should be short and lower-case, and separated with underscores if improving readability as shown below:

my1stmod.py my_1st_mod.py myfirstmodule.py my_first_module.py 

import my1stmod import my_1st_mod import myfirstmodule import my_first_module 

A package name should be short and lower-case, and separated with underscores if really improving readability as shown below:

*Memo:

• Basically, underscores shouldn't be used.

my1stpkg my_1st_pkg myfirstpackage my_first_package 

import my1stpkg import my_1st_pkg import myfirstpackage import my_first_package 

A single, double and triple leading and trailing underscore can be used with variables, methods and classes as shown below:

*Memo:

• A single leading underscore(_abc) can make the unforced private attributes(variables, methods and classes) in a class which are basically used in a class so they're still acceptable from the outside of the class.
• A double leading underscore(__abc) can make the forced private attributes in a class which are only used in the class so it's unacceptable from the outside of the class.
• A double leading and trailing underscore(__abc__) can make the special public attributes which are used in and out a class, e.g. __init__, __class__, __name__, etc.
• A single trailing underscore(abc_) is used to prevent identifier conflicts when using the identifiers (including reserved keywords) which already exist, e.g. var_, func_, len_, list_, int_, True_, def_, class_, etc.

class Cls: _var = "_var" # (Acceptable)  __var = "__var" # (Unacceptable)  var_ = "var_" # (Acceptable)  __var__ = "__var__" # (Acceptable)  def _func(self): pass # (Acceptable)  def __func(self): pass # (Unacceptable)  def func_(self): pass # (Acceptable)  def __func__(self): pass # (Acceptable)  class _Cls: pass # (Acceptable)  class __Cls: pass # (Unacceptable)  class Cls_: pass # (Acceptable)  class __Cls__: pass # (Acceptable)  cls = Cls() print(cls._var) # _var print(cls.__var) # Error print(cls.var_) # var_ print(cls.__var__) # __var__  print(cls._func.__name__) # _func print(cls.__func.__name__) # Error print(cls.func_.__name__) # func_ print(cls.__func__.__name__) # __func__  print(cls._Cls().__class__.__name__) # _Cls print(cls.__Cls().__class__.__name__) # Error print(cls.Cls_().__class__.__name__) # Cls_ print(cls.__Cls__().__class__.__name__) # __Cls__