Count the number of occurences of letters in a Python string

So I got a DNA sequence.

ACCAGAGCGGCACAGCAGCGACATCAGCACTAGCACTAGCATCAGCATCAGCATCAGC
CTACATCATCACAGCAGCATCAGCATCGACATCAGCATCAGCATCAGCATCGACGACT
ACACCCCCCCCGGTGTGTGTGGGGGGTTAAAAAT开发者_如何学PythonGATGAGTGATGAGTGAGTTGTGTG
CTACATCATCACAGCAGCATCAGCATCGACATCAGCATCAGCATCAGCATCGACGACT
TTCTATCATCATTCGGCGGGGGGATATATTATAGCGCGCGATTATTGCGCAGTCTACG
TCATCGACTACGATCAGCATCAGCATCAGCATCAGCATCGACTAGCATCAGCTACGAC

I need to count the bases.

Also for some reason it can sometimes it can alternate between upper or lowercase in the same string.

for base in 'ACGT':
  print base, thesequence.count(base) + thesequence.count(base.lower())