Problem
A string is simply an ordered collection of symbols selected from some alphabet and formed into a word; the length of a string is the number of symbols that it contains.
An example of a length 21 DNA string (whose alphabet contains the symbols 'A', 'C', 'G', and 'T') is "ATGCTTCAGAAAGGTCTTACG."
Given: A DNA string ss of length at most 1000 nt.
Return: Four integers (separated by spaces) counting the respective number of times that the symbols 'A', 'C', 'G', and 'T' occur in ss.
Sample Dataset
AGCTTTTCATTCTGACTGCAACGGGCAATATGTCTCTGTGTGGATTAAAAAAAGAGTGTCTGATAGCAGC
Sample Output
20 12 17 21 方法一：
f = 'AGCTTTTCATTCTGACTGCAACGGGCAATATGTCTCTGTGTGGATTAAAAAAAGAGTGTCTGATAGCAGC'
for i in f:
b = list(f) # 把‘AAA’变成 ['A','A'',A']
c = {}
for i in b:
c[i] = b.count(i) # 把key 和value 写入字典，如 A：1
print (c.values()) # 最后的结果为 [20,12,21,17]
方法二：
f = 'AGCTTTTCATTCTGACTGCAACGGGCAATATGTCTCTGTGTGGATTAAAAAAAGAGTGTCTGATAGCAGC'
counts = []
for i in ['A','C','G','T']: # 把输出的顺序定好
counts.append(f.count(i))
print ('\t'.join(map(str, counts))) #map() 这里的意思是吧输出的[20,12,17,21]变为 20 12 17 21