Python Overview Class 11 - Day 2

  Python Character Set 

• Character set is the set of valid characters that a language can recognize. 
• A character represents any letter, digit or any other symbol. 
• Python has the following character sets: ·
• Letters – A to Z, a to z · Digits – 0 to 9 
• Special Symbols - + - * / etc. 
• Whitespaces – Blank Space, tab, carriage return, newline, formfeed 
• Other characters – Python can process all ASCII and Unicode characters as part of data or literals.

 Tokens

• In a passage of text, individual words and punctuation marks are called tokens or lexical units or lexical elements. 
• The smallest individual unit in a program is called token or lexical unit
•  Python has the following tokens:

1.  Keyword 
2.  Identifiers 
3.  Literals 
4.  Operators 
5.  Punctuators

 

 

1. Keywords ( Reserved words)

A keyword is a word having a special meaning reserved by the programming language

• They convey special meaning to the language compiler/interpreter.
• Reserved for special purpose and must not be used as a normal identifier name  

2. Identifiers( Names )

• Identifiers are  are names used to identify a variable, functions, objects, classes, lists, dictionaries or other entities in a program
• These are the rules for forming an Identifier in Python
• The name should begin with uppercase or lowercase alphabet or an underscore sign(_). This may be followed by any combination of characters a-z, A-Z, 0-9 or underscore(_). Note: Name or Identifier cannot start with a digit.
• It can be of any length but keep it short and meaningful 
• Python is case sensitive as it treats uppercase and lowercase characters differently
• Must not be a Keyword or reserved word ( verify Keyword table given above)
• Cannot have special symbols like !, @, #, $, % etc Note: Only _ is allowed

Valid Identifiers:

Meaningful Names:

  Invalid Identifiers: