Keywords and Identifier

Identifier is the name given to entities like class, functions, variables etc. in Python. It helps differentiating one entity from another.An identifier starts with a letter A to Z or a to z or an underscore (_) followed by zero or more letters, underscores and digits (0 to 9).
Python doesn’t allow punctuation characters such as %,$ and @ within identifiers.It is a case sensitive language.

Rules for writing identifiers in Python:-
* First character must be a letter or underscore ( _ ).
* Starting an identifier with a single leading underscore indicates by convention that the identifier is meant to be private.
* Starting an identifier with two leading underscores indicates a strongly private identifier.
* Any additional character can be a letter or underscore.
* Case sensitive.(always mind it)
* It can begin with a number also.
* Identifier can be of any length.

Keywords are the reserved words in Python. We cannot use a keyword as variable name, function name or any other identifier. They are used to define the syntax and structure of the Python language. All the Python keywords contain lowercase letters only.

Keywords in Python programming language
False	class	finally	is	return
None	continue	for	lambda	try
True	def	from	nonlocal	while
and	del	global	not	with
as	elif	if	or	yield
assert	else	import	pass
break	except	in	raise

you can also use command line prompt to know about keywords,just write help() and press enter then write keywords,press enter.
It will produce following result…
You can take help to know about any keywords of it by writing name as shown in list.