complementary_strand

'''This program intends to produce a
DNA complementary string, taking into
account the translation and 5' 3' inversion.
'''
def compl_dna(sequence):
      sequence = sequence.upper()
      seq = sequence[::-1] #inverted sequence
      seq = list(seq)


      i = 0
      for nuc in seq:
            if seq[i] == 'G':
                  seq[i] = 'C'
            elif seq[i] == 'C':
                  seq[i] = 'G'
            elif seq[i] == 'T':
                  seq[i] = 'A'
            elif seq[i] == 'A':
                  seq[i] = 'T'
            i += 1
      
      print(f'{seq}')

#starting the program
print('Welcome! This program will give you the complementary DNA strand to your data. ')

#asking the user
choice = int(input('Type 1 to enter the .txt file pathway or 2 to paste your sequence: '))

if choice == 1:
    dir_pathway = input('Type the file pathway. If it is already on this program file, just type <filename.txt>: ')
    file = open(f"{dir_pathway}", 'r')
    sequence_nuc = file.read()
elif choice == 2: 
    sequence_nuc = input('Paste your sequence here: ')

compl_dna(sequence_nuc)

if choice == 1: 
  file.close()