IDENTIFIERS
- A Name in Python Program is called Identifier.
- It can be Class Name OR Function Name OR Module Name OR Variable Name.
- a = 10
Rules to define Identifiers in Python:
1. The only allowed characters in Python are
- alphabet symbols(either lower case or upper case)
- digits(0 to 9)
- underscore symbol(_)
By mistake, if we are using any other symbol like $ then we will get a syntax error.
- cash = 10 √
- ca$h =20 X
2. Identifier should not starts with digit.
- 123total X
- total123 √
3. Identifiers are case-sensitive. Of course, Python language is a case-sensitive language.
- total=10
- TOTAL=999
- print(total) #10
- print(TOTAL) #999
Identifier:
1) Alphabet Symbols (Either Upper case OR Lower case)
2) If Identifier is start with Underscore (_) then it indicates it is private.
3) Identifiers should not start with Digits.
4) Identifiers are case-sensitive.
5) We cannot use reserved words as identifiers
Eg: def = 10 X
6) There is no length limit for Python identifiers. But not recommended to use too
lengthy identifiers.
7) Dollor ($) Symbol is not allowed in Python.
Q) Which of the following are valid Python identifiers?
1) 123total X
2) total123 √
3) java2share √
4) ca$h X
5) _abc_abc_ √
6) def X
7) if X
Note:
1) If the identifier starts with _ symbol then it indicates that it is private
2) If identifier starts with __(Two Under Score Symbols) indicating that strongly private
identifier.
3) If the identifier starts and ends with two underscore symbols then the identifier is
a language-defined special name, which is also known as magic methods.
4) Eg: __add__