Python Keywords & Identifiers

    This tutorial has everything about python keywords and identifiers which is the most important part of every programming languages.

    Let’s start with What is Python Keyword?

    Python Keywords

    Every programming language has some words which are reserved, with special meanings, and you can not use those names randomly. Those words are known as Keywords.

    In Python 3 versions there is a total of 32 reserved keywords. So, whenever you write a variable make sure that it's not a reserved keyword or else the python interpreter will give an error.

    For example: if is a reserved keyword means we can not use it as a variable or identifier.

    >>> if = 34
      File "<stdin>", line 1
        if = 34
           ^
    SyntaxError: invalid syntax

    All the Python Keywords are case-sensitive which means a word in python will act as a keyword if you write it as it is supposed to.

    E.g.

    Correct

    def function_1(): 
        pass

    Wrong

    DeF function_1():  #it will through an Error

    SyntaxError: invalid syntax def is a keyword used in python to declare a function, instead of def if you write DeF then it will generate a Syntax Error: invalid syntax Exception, you need to write the keywords as they are supposed to write and as they were defined in Python. The Keywords in the python are in lower case except for these three True, False and None

    Python Reserved Keywords

    and

    as

    assert

    break

    class

    continue

    def

    del

    elif

    else

    except

    False

    finally

    for

    from

    global

    if

    import

    in

    is

    lambda

    None

    nonlocal

    not

    or

    pass

    raise

    return

    True

    try

    while

    with

    yield

    Python Identifiers or Python variables

    In Python when you declare a class, or a function or a variable, you give it a name and that could be anything according to you.

    Those names are known as Identifiers by which you identify your class, functions or variables. Identifiers are the opposite of the Keywords. Identifiers are not reserved in python. You can give any name to the identifiers which you suit, but there are some set of rules to write an identifier or variable name. Identifiers are case-sensitive too for e.g.

    Note: Python identifiers are also known as Python variables. The term identifers and variables are used interchangeably.

    variable = 2
    Variable =3
    print(variable)
    print(Variable)

    Output

    2
    3

    In the above example we have defined 2 variables, first is variable and the 2nd is Variable and both are different.

    As we have mentioned above that, there are some sets of rules for writing an Identifier.

    Rules To write an Identifier

    • An identifier can be a combination of alphabets that is lowercase (a to z) or uppercase (A to Z)) or digits(0 to 9) or an underscore(_).
    • You can not use a digit or any special character except underscore (_) to start an identifier name.
    • You cannot use any special symbol to write an Identifier.
    • You cannot give blank space to write an identifier.
    • You cannot use a reserved keyword to write an identifier.

    E.g.

    Variable23 = 44  # Valid Identifier
    23Variable = 44  #Invalid Identifier start with a digit
    _23Variable = 44  #Valid variable start with underscore
    Variable 23 = 44  # Invalid blank space between Variable and 23
    Variable@ 23 = 44  # Invalid blank it contains a special symbol @
    Variable_23 = 44  #Valid there is no space in between the identifier
    False = 44  #Invalid Identifier False is a Keyword

    Conclusion

    Python keywords are reserved words or names which perform some specific task or have a special meaning. Python keywords can not be used as a variable name. On the other hand, if we want to give a name to a value, class, function, or object we can use the identifiers.

    Point to Remember

    • Python is case-sensitive, so be careful while using cases.
    • The Identifiers could be of any length.
    • Always use underscore when you write a lengthy identifier.