Keywords and Identifiers in Python 3
By Lenin Mishra
Python Keywords
Python has a bunch of reserved words. These are known as Python keywords. These keywords can’t be used to name objects in Python like variables, functions and classes.
Keywords in Python are case-sensitive.
The following is a list of reserved keywords in Python 3.9.
False await else import pass
None break except in raise
True class finally is return
and continue for lambda try
as def from nonlocal while
assert del global not with
async elif if or yield
Simple use of if-else in Python
Code
num = 5
if num%2 == 0:
print("It is Even")
else:
print("It is odd")
Output
It is odd
How to check if a string is a keyword?
Python provides a keyword
module that allows you to check for reserved keywords.
Code/Output
import keyword
print(keyword.iskeyword("for"))
>>> True
print(keyword.iskeyword("str"))
>>> False
You could also get a list of all reserved keywords in Python.
Code/Output
import keyword
print(keyword.kwlist)
>>> ['False', 'None', 'True', '__peg_parser__', 'and', 'as', 'assert', 'async', 'await', 'break', 'class', 'continue', 'def', 'del', 'elif', 'else', 'except', 'finally', 'for', 'from', 'global', 'if', 'import', 'in', 'is', 'lambda', 'nonlocal', 'not', 'or', 'pass', 'raise', 'return', 'try', 'while', 'with', 'yield']
Python Identifiers
Identifiers are opposite of reserved keywords. They are just names that users can choose to name their variables, functions and classes.
Rules to remember while writing identifiers
Can be a combination of lowercase and uppercase letters(
A to Z
), numbers(0 to 9
) and underscore(_
).Valid Examples -
x
,my_list
,str123
Cannot start with a number.
Invalid example -
1name
Valid Example -
name1
Keywords cannot be used as identifiers
for = 1 >>> SyntaxError: invalid syntax
Special symbols like !, @, #, $, % etc. cannot be used
x@ = 1 >>> SyntaxError: invalid syntax
Final Suggestions
- Python is case sensitive. This means
X
andx
are not the same. - Use variable, function and class names that is descriptive of it’s functionality.
- Use snake case to write long variables. Example -
my_int_only_list
.