Identifiers are the names given to the fundamental building blocks in a program.
These can be variables ,class ,object ,functions , lists , dictionaries etc.
There are certain rules defined for naming i.e., Identifiers.
I. An identifier is a long sequence of characters and numbers.
II.No special character except underscore ( _ ) can be used as an identifier.
III.Keyword should not be used as an identifier name.
IV.Python is case sensitive. So using case is significant.
V.First character of an identifier can be character, underscore ( _ ) but not digit.