DNA - Getting the highest key value from a defaultdict

Question

I have come a bit on DNA and have managed to write an algorithm for adding the number of matches in the sequence to a defaultdict. But I'm having problems with how to get the maximum value from the defaultdict where I'm storing the key and values. I've marked the section where I need help with "need help here" in the code. Would appreciate any help greatly!

import csv
import sys
from collections import defaultdict

# Check that two command line arguments are passed with the program (database and sequence to test)
if len(sys.argv) != 3:
    print("Error: Input one CSV file and one .txt file")
    exit(1)

# Store argv inputs into variables
csvfile = sys.argv[1]
sequencefile = sys.argv[2]

#Open CSV file and read into memory
csv_file = open (csvfile, "r")
csv_reader = csv.DictReader(csv_file)

# Read into the specific fields of the CSV file (for later out branching out the STRs)
fields = csv_reader.fieldnames
print(fields)
print(len(fields))

# Store the different STRs in variables
STRs = fields[1:] # Removes the name column and store it in a new variable
print(STRs)

# Open sequence file
sequence_file = open (sequencefile, "r")
sequence_reader = sequence_file.read()
print("Sequence: ", sequence_reader)
sequence_file.seek(0)

# Create a dict to store each index in the DNA sequence (key), and it's count for current STRs (value)
d = defaultdict(int)

# Create a dict to store each STR (key) and the longest consecutive repeat of it in the sequence (value)
e = {}

for x in STRs:
    for counter, y in enumerate(sequence_reader):

        # Read in a chunk of len(x) from sequence file, store it in current_chunk
        print(counter)
        sequence_file.seek(counter)
        current_chunk = sequence_file.read(len(x))
        print(y, x, current_chunk)

        # While current_chunk == x, increment the counter in the dict with 1, read in next chunk
        index = counter #Add a index to move forward checking next chunk in the sequence
        iteration = 1
        while current_chunk == x:
            print("current chunk: ", current_chunk)
            print("x: ", x)
            print("match!")
            d[counter] += 1
            currentindex = index + (iteration * len(x))
            sequence_file.seek(currentindex)
            current_chunk = sequence_file.read(len(x))
            iteration += 1
    # Store the highest count for the current STR
        # Get the highest value from the "d" array and store it in a variable "high"
            # ------------------------ NEED HELP OVER HERE ------------------------

        # Add one instance to the "e" array with key = Current STR (x) and value = "high"

# Compare each person in the database with the numbers in the "e" array

# Print out the match, or if no match, print out no match

Answer 1

If you just want the highest value from a dict and you don't care about what key it's associated with, you can just do:

max_value = max(d.values())

For the key of the max value:

max_key = max(d, key=d.get)

If you want both in a pair:

max_tuple = max(d.items(), key=lambda k: k[1])