Python Lexical Analyzer

This Python program is a lexical analyzer of a custom programming language. The program interface is implemented through PyQT.

How the program works:

The user enters a program code into the input field of the interface. After clicking on the "Start" button, the entire contents of the line is transferred to the "temp.txt" file. The program takes data from a file and processes it by performing lexical analysis.

Sample input code for analysis:

{ a := 9; b := 33; /* Comment */ c := a plus b; }

The Backus-Naur forms are listed below:

• character ::= A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | a | b | c | d | e | f | g | h | i | j | k | l | m | n | o | p | q | r | s | t | u | v | w | x | y | z
• number ::= 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9
• integer ::= binary | octal | decimal | hexadecimal
• binary ::= {/ 0 | 1 /} (B | b)
• octal ::= {/ 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 /} (O | o)
• decimal ::= {/ number /} [D | d]
• hexadecimal ::= number {number | A | B | C | D | E | F | a | b | c | d | e | f} (H | h)
• real ::= numeric_string index | [numeric_string] . numeric_string [index]
• numeric_string ::= {/ number /}
• index ::= ( E | e ) [ + | - ] numeric_string
• program ::= «{» {/ (description | operator) ; /} «}»
• description ::= {identifier {, identifier } : type ;}
• type ::= % | ! | $
• compound ::= begin operator { ; operator } end
• assignment ::= identifier := expression
• conditional ::= if «(»expression «)» operator [else operator]
• fixed_cycle ::= for assignment to expression [step expression] operator next
• conditional_loop ::= while «(»expression «)» operator
• input ::= readln identifier {, identifier }
• output ::= writeln expression {, expression }
• comment_start ::= «/*»
• comment_end ::= «*/»
• relation_group_operations ::= NE | EQ | LT | LE | GT | GE
• addition_group_operations :: = plus | min | or
• multiplication_group_operations ::= mult | div | and
• unary_operation ::= ~
• expression ::= operand {relation_group_operations operand}
• operand ::= term {addition_group_operations term}
• term ::= multiplier {multiplication_group_operations multiplier}
• multiplier ::= identifier | number | boolean_constant | unary_operation multiplier | «(»expression«)»
• number ::= integer | real
• boolean_constant ::= true | false
• identifier ::= character {character | number}