DNA python

dna.py

from __future__ import division

print '\nExample 1'

# Input DNA 1
dna = "ACTGATCGATTACGTATAGTATTTGCTATCATACATATATATCGATGCGTTCAT"
print 'DNA:', dna

# Calculate AT count
A_count = dna.count("A")
T_count = dna.count("T")
AT_count = A_count + T_count
print 'AT count:', AT_count
dna_length = len(dna)
print 'DNA length:', dna_length

# Calculate AT content percentage
AT_content = AT_count / dna_length
print 'AT percentage:', AT_content * 100

print '\nExample 2'

# Work out complement DNA
complement_dna_B = dna.replace("A", "B")
complement_dna_D = complement_dna_B.replace("C", "D")
complement_dna_E = complement_dna_D.replace("G", "C")
complement_dna_F = complement_dna_E.replace("T", "A")
complement_dna_G = complement_dna_F.replace("B", "T")
complement_dna = complement_dna_G.replace("D", "G")
print 'Complement DNA:', complement_dna

print '\nExample 3'

# Input DNA 2
restriction_dna = "ACTGATCGATTACGTATAGTAGAATTCTATCATACATATATATCGATGCGTTCAT"
print 'DNA:', restriction_dna
restriction_position = restriction_dna.find("GAATTC")

fragment_size_1 = len(restriction_dna[0:restriction_position])
cut_site = 1
fragment_size_3 = fragment_size_1 + cut_site

print 'Fragment 1 size:', fragment_size_3
total = len(restriction_dna)
print 'DNA length:', total
fragment_size_4 = total - fragment_size_3
print 'Fragment 2 size:', fragment_size_4