#import numpy as np
#import pandas as pd
#import matplotlib.pyplot as plt #visualization
#import seaborn as sns #modern visualization
#import pandas.io.sql
#import pyodbc
#import csv
import re

#checksum for GST:
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def validGSTnum():
#create dictionaries
    #place_value
    integers='0123456789'
    int_placevalue = dict()
    count=0
    for int in integers:
        int_placevalue[int] = count
        count +=1

    charaters='ABCDEFGHIJKLMNOPQRSTUVWXYZ'
    char_placevalue = dict()
    count=10
    for char in charaters:
        char_placevalue[char] = count
        count +=1

    int_placevalue.update(char_placevalue)
    place_value=int_placevalue


    state_codes= {'01':'JAMMU AND KASHMIR','20':'JHARKHAND','02':'HIMACHAL PRADESH','21':'ODISHA','03':'PUNJAB','22':'CHATTISGARH',
    '04':'CHANDIGARH','23':'MADHYA PRADESH','05':'UTTARAKHAND','24':'GUJARAT','06':'HARYANA','25':'DAMAN AND DIU','07':'DELHI',
    '26':'DADRA AND NAGAR HAVELI','08':'RAJASTHAN','27':'MAHARASHTRA','09':'UTTAR  PRADESH','28':'ANDHRA PRADESH (old)',
    '10':'BIHAR','29':'KARNATAKA','11':'SIKKIM','30':'GOA','12':'ARUNACHAL PRADESH','31':'LAKSHWADEEP','13':'NAGALAND',
    '32':'KERALA','14':'MANIPUR','33':'TAMIL NADU','15':'MIZORAM','34':'PUDUCHERRY','16':'TRIPURA',
    '35':'ANDAMAN AND NICOBAR ISLANDS','17':'MEGHLAYA','36':'TELANGANA','18':'ASSAM','37':'ANDHRA PRADESH (NEW)','19':'WEST BENGAL'}

    #Enter GST number
    #gst_number=input("Enter GST Regestration Number:\n")
    #print(gst_number)
    gst_number = "22ALJPT5243L1ZS"
    print("GST Number:",gst_number)

    #check GST no is format specific
    regex = re.compile('[`@_!#$%^&*()<>?/\|}{~:]')
    substring = regex
    search = re.search(substring,gst_number)

    if len(gst_number)==15 and regex.search(gst_number) == None:
        list_of_nums_int = re.findall('\d+', gst_number)
        list_of_char_str = re.findall('[a-zA-Z]+', gst_number)

        state_code = list_of_nums_int[0]
        print('Your GST number state code:', state_code)
        pannumber_char = list_of_char_str[0] + list_of_nums_int[1] + list_of_char_str[1]
        print('Your GST number PAN code:', pannumber_char)
        entity_number = list_of_nums_int[2]
        print('Entity number of the PAN holder:', entity_number)
        checksum_digit = list_of_char_str[2]
        print('Checksum digit of this GST number', checksum_digit)

        if state_code in state_codes:
            if len(pannumber_char) == 10 and type(pannumber_char)==str:
                if type(entity_number)==int or type(entity_number)==str:
                    if gst_number[13]=='Z':
                        if type(checksum_digit)==int or type(checksum_digit)==str:
                            print("\nThis GST number is format specific")
                            pass
                            #info from this GST num
                            state_info=state_codes[state_code]
                            print('\nThis GST code corresponds to',state_info)
                            #check if GST number is valid
                            odd_digits=[]
                            even_digits=[]
                            for index in range(0,13,2):
                                factor=1
                                x=place_value[gst_number[index]]*factor
                                quotient = x//36
                                remainder = x%36
                                odd_digits.append(quotient+remainder)
                            for index in range(1,14,2):
                                factor=2
                                y=place_value[gst_number[index]]*factor
                                quotient=y//36
                                remainder=y%36
                                even_digits.append(quotient+remainder)
                            total=sum(odd_digits)+sum(even_digits)
                            z=total%36
                            a=(36-z)%36
                            if a==place_value[gst_number[14]]:
                                print("\nThis GST number is valid")
                            else:
                                print("\nThis GST number is format specific but invalid")
    elif len(gst_number)==15:
        print("This GST number contains special characters")
        match = search.group()
        index = search.start()
        print("Found", match, "at position", index+1)

    else:
        print("This GST number is invalid")
        return 0

validGSTnum()
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