Counting DNA Nucleotides

We can write a function to easily get the count of the letters of a string. We use a Python dictionary to store and count the DNA string nucleotides:

def dna_nucleotide_count(dna_string: str) -> str:
    """
    Parameters
    ----------
    dna_string : Str
    DNA Nucleotide String (DNA String)   
    
    Returns 
    -------
    Dictionary
    Count of each of the bases adenine, cytosine, guanine, and thymine
    
    Example
    -------
    Input: AGCTTTTCATTCTGACTGCAACGGGCAATATGTCTCTGTGTGGATTAAAAAAAGAGTGTCTGATAGCAGC
    Output: {'A': 20, 'G': 17, 'C': 12, 'T': 21}
    """
    nucleotide_count = {}
    for base in dna_string:
        if base in nucleotide_count: #Create nucleotide counter or add one to nucleotide already existing
            nucleotide_count[base] += 1
        else:
            nucleotide_count[base] = 1
    
    return nucleotide_count

print(dna_nucleotide_count('AGCTTTTCATTCTGACTGCAACGGGCAATATGTCTCTGTGTGGATTAAAAAAAGAGTGTCTGATAGCAGC'))

## {'A': 20, 'G': 17, 'C': 12, 'T': 21}

I manually put them in the right order based on the expected input. Two other methods from the solutions section that were particularly interesting were:

def qt(s):
      return s.count("A"), s.count("G"), s.count("C"), s.count("T")

and

print(*map(input().count, "ACGT"))