(Python Tutorial – 003)
Python Keywords and Identifiers
In this tutorial, you will learn about keywords (reserved words in Python) and identifiers (names given to variables, functions, etc.).
Python Keywords
Keywords are the reserved words in Python.
We cannot use a keyword as a variable name, function name or any other identifier. They are used to define the syntax and structure of the Python language.
In Python, keywords are case sensitive.
There are 33 keywords in Python 3.7. This number can vary slightly over the course of time.
All the keywords except True
, False
and None
are in lowercase and they must be written as they are. The list of all the keywords is given below.
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 |
Looking at all the keywords at once and trying to figure out what they mean might be overwhelming.
If you want to have an overview, here is the complete list of all the keywords with examples.
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Python Identifiers
An identifier is a name given to entities like class, functions, variables, etc. It helps to differentiate one entity from another.
Rules for writing identifiers
- Identifiers can be a combination of letters in lowercase (a to z) or uppercase (A to Z) or digits (0 to 9) or an underscore
_
. Names likemyClass
,var_1
andprint_this_to_screen
, all are valid example. - An identifier cannot start with a digit.
1variable
is invalid, butvariable1
is a valid name. - Keywords cannot be used as identifiers.
global = 1
Output
File "<interactive input>", line 1 global = 1 ^ SyntaxError: invalid syntax
- We cannot use special symbols like !, @, #, $, % etc. in our identifier.
a@ = 0
Output
File "<interactive input>", line 1 a@ = 0 ^ SyntaxError: invalid syntax
- An identifier can be of any length.
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Things to Remember
Python is a case-sensitive language. This means, Variable
and variable
are not the same.
Always give the identifiers a name that makes sense. While c = 10
is a valid name, writing count = 10
would make more sense, and it would be easier to figure out what it represents when you look at your code after a long gap.
Multiple words can be separated using an underscore, like this_is_a_long_variable
.
Disclaimer: The information and code presented within this recipe/tutorial is only for educational and coaching purposes for beginners and developers. Anyone can practice and apply the recipe/tutorial presented here, but the reader is taking full responsibility for his/her actions. The author (content curator) of this recipe (code / program) has made every effort to ensure the accuracy of the information was correct at time of publication. The author (content curator) does not assume and hereby disclaims any liability to any party for any loss, damage, or disruption caused by errors or omissions, whether such errors or omissions result from accident, negligence, or any other cause. The information presented here could also be found in public knowledge domains.
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