Python Keywords and Identifiers

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The main aim of this post is to make you familiar with the Python keywords and identifiers. An individual must know everything about them as these are the fundamental building blocks of Python Programming.

Python keyword is referred to as a unique programming term that has been intended to perform some action. There are about 33 such keywords in Python, each of which serves a different purpose. Simultaneously, they build up the vocabulary of the Python programming language.

These represent the syntax as well as the structure of a Python program. As all of these are reserved, therefore you cannot make use of their names to define variables, functions or classes. Let us now see more about Python Keywords.

Python Keywords

Python Keywords are the special words that are reserved and hold a specific meaning. Python comprises of a set of keywords that cannot be used as variables in programs. All keywords in Python are highly case sensitive. Thus, you should be careful while using those keywords in your code. The list of the Python keywords is quite long to be remembered at once but we have mentioned below all the keywords with the key purpose being

To provide the readers with an initial idea of the keywords available. An individual doesn’t need to jump onto memorize these keywords instead the must try to learn using those step by step. One more point that should be noted is that the list of the Python keywords mentioned below may vary. The language might get away with few of the old keywords and that would bring in the newer ones in future releases. Hence, in order to get hold of the up-to-date list, one shall open the Python shell and then run the following commands as mentioned in the below snippet.

help> keywords

Here is a list of the Python keywords.  Enter any keyword to get more help.

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

help>

Alternatively, you may make use of the Python’s keyword module and import it directly from the shell and then run the below commands to seek the supported keywords.

>>> import keyword
>>> keyword.kwlist
['False', 'None', 'True', 'and', 'as', 'assert', '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']
>>>

Back to list

Python Identifiers

Python Identifiers refer to the user-defined names for representing a function, variable, class, module or some other object. In case you assign any name to the programmable entity in Python, then, in that case, it is nothing but is called an identifier technically.

Python programming language lays down a certain set of rules for the programmers in order to create some meaningful identifiers.

Guidelines For Creation of Identifiers in Python

1. To form an identifier and make use of a sequence of letters either in the lowercase (i.e. a to z) or in the uppercase (i.e. A to Z). However, one can also mix up the digits (0 to 9) or use an underscore (_) while writing the identifier.

For example – Names such as shape_1, shape class, and also upload_shape_to_db are the valid identifiers.

2. One may make use of the digits to start with an identifier name. It’ll result in the syntax error.

For example – The name, 0Shape is an incorrect identifier, but shape1 is a valid identifier.

3. Since the Keywords are reserved, therefore one shall not make use of those as identifiers.

>>> for=1
SyntaxError: invalid syntax
>>> True=1
SyntaxError: can't assign to keyword

SyntaxError: can’t assign to keyword

4. Also, Python Identifiers can not comprise of the special characters (i.e. ‘.’, ‘!’, ‘#’, ‘$’, ‘@’, ‘%’) within their formation. Such symbols are usually forbidden.

>>> @index=0
SyntaxError: invalid syntax
>>> isPython?=True
SyntaxError: invalid syntax

5. Python doc implies that one can have an identifier accompanied with unlimited length. But this is just half the truth. Making use of a large name (i.e. more than 79 chars) would result in the violation of a rule that has been set by the PEP-8 standard. It says. One must keep all the lines limited up to a maximum of 79 characters.

Testing if An Identifier is Valid

One can test whether a Python identifier is valid or not by making use of the keyword.iskeyword() function. It would return “True” in case the keyword is correct and if not it would otherwise return “False”.

Please refer to the snippet below.

>>> import keyword
>>> keyword.iskeyword("aptron")
False
>>> keyword.iskeyword("try")
True
>>>

Another useful way to check whether an identifier is valid or not is to use the str.isidentifier() function. But this is available only in Python 3.0 and onwards.

>>> 'aptronnoida'.isidentifier()
True
>>> '1aptronnoida'.isidentifier()
False
>>> 'aptronnoida.in'.isidentifier()
False
>>> 'aptronnoida_in'.isidentifier()
True

Best Practices For Naming an Identifier

  • It is better to have class names that begin with a capital letter. All the other identifiers must start with a lowercase letter.

  • One shall declare the private identifiers by making use of the (‘_’) underscore as the first letter while naming an identifier.

  • Do not make use of ‘_’ as the trailing and leading character within an identifier as the Python built-in types already make use of this notation.

  • Avoid making use of the names that consist of only a single character rather, make use of some meaningful names.

    • For example – If i = 1 is valid, but writing index = 1 or iter = 1 or would make better sense.

  • You may use underscores in order to combine multiple words for forming some sensible name.

    • For example – count_no_of_letters

After going through the above post, you may now have a considerable idea of how the keywords and identifiers work in Python. We have made all the possible efforts to cover all the important details about and so one can learn fast and make use of them efficiently.

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