- A name in python program is called identifier.
- Identifiers can be class name or function name or module name or variable name.
- Example a = 10, where a is identifier.
Identifiers naming
- 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 syntax error.
Example
Python
cash = 10
print(cash)Output
PowerShell
10Example
Python
ca$h = 20
print(ca$h)Output
PowerShell
SyntaxError: invalid syntax- Identifier should not starts with digit.
Example
Python
123total = 10
print(123total)Output
PowerShell
SyntaxError: invalid decimal literalExample
Python
total123 = 10
print(total123)Output
PowerShell
10- Identifiers are case sensitive. Of course python language is case sensitive language.
Python
total=10
TOTAL=999
print(total)
print(TOTAL)Output:
PowerShell
10
999- We cannot use reserved words as identifiers.
Python
def = 10Output
PowerShell
SyntaxError: invalid syntax- There is no length limit for python identifiers. But not recommended to use too lengthy identifiers.
Python
ABCDEFGHIJKLMNOPQRSTUVWXYS = 10
print(ABCDEFGHIJKLMNOPQRSTUVWXYS)Output
PowerShell
10Question
Which of the following are valid python identifiers?
Python
123total = 10
total123 = 10
java2share = 10
ca$h = 10
abc_abc = 10
def = 10
if = 10Answer
PowerShell
123total = 10 ❌
total123 = 10 ✔
java2share = 10 ✔
ca$h = 10 ❌
abc_abc = 10 ✔
def = 10 ❌
if = 10 ❌Remark
- If identifier starts with _ symbol then it indicates that it is private.
- If identifier starts with __(two under score symbols) indicating that strongly private identifier.
- If the identifier starts and ends with two underscore symbols then the identifier is language defined special name, which is also known as magic example __add__.
Ungraded Questions
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