Example solution for pattern_count() and reading from a dataset

def pattern_count(sequence, pattern):
    count = 0
    for i in range(len(sequence) - len(pattern) +1):
        if sequence[i:i+len(pattern)] == pattern:
            count += 1
    return count

# the path to the dataset is the first argument
import sys
dataset_file = sys.argv[1]

with open(dataset_file) as f:
    sequence = f.readline()[:-1]
    pattern = f.readline()[:-1]

print(pattern_count(sequence, pattern))