Indentifiers in Python

 

Identifiers

In python, Identifiers are the names given to any variable, function, class, object or module.

These names are given by programers. Identifiers are used to uniquely identify these in our code. 

Rules to define Identifiers :

• Identifiers can only contain letters (a-z, A-Z), digits (0-9), and underscores (_).
• Identifiers must not start with a digit. 
• Identifiers are case-sensitive (`myVar` and `myvar` are different).
• And we cannot use reserved words / keywords as indentifiers.
•  There is no length limit for Python identifiers. But not recommended to use too lengthy identifiers.
• We must use descriptive and meaningful names for better code readability.

Example : 

name = "Alice"

_age = 25

total_amount1 = 100.50

In the above Example, there is no output. But here 'name', '_age' and 'total_amount1' are identifiers. These are valid identifiers.

Question : Find the valid identifiers from below list.

• cash = 10
• cash$ = 15
• all!hands = 30
• total123 = 100
• 123total = 100
• if = 33
• _abc_abc_ = 22
• def = 44 

Answer :

cash = 10   #It is a valid Identifier

cash$ = 15  #Invalid because '$'is not allowed as valid identifier

all!hands = 30  #Invalid because '!'is not allowed as valid identifier

total123 = 100  #Valid

123total = 100 #Invalid because Indentifier must not start with a digit

if = 33 #Invalid because we can not use keyword (if) as Identifier

_abc_abc_ = 22   #Valid

def = 44  #Invalid because we can not use keyword (def) as Identifier

Usage of Identifier :

• Assign values to variables: `age = 25`
• Define functions: `def calculate_sum():`
• Name classes: `class Student:`
• Reference modules and objects

Best Practices :

• Use descriptive and meaningful names (e.g., `total_price` instead of `tp`).
• Use lowercase letters for variable and function names (e.g., `student_name`).
• Use uppercase letters for constants (e.g., `PI = 3.14`).
• Use underscores to separate words in identifiers (`snake_case`).
• Avoid using single-character names except for counters or iterators.
• Never use Python reserved keywords as identifiers.