Program for dna not printing anything

Question

I have written a program for DNA, but it's not printing anything. Code:

import csv
from sys import *

if len(argv) != 2:
    print("Usage: python dna.py data.csv sequence.txt")

def maxcount(n, main, seq):
    l = len(main)
    maxc = 0
    currc = 0
    for i in range(n):
        cp = i
        while seq[cp : cp + l]:
            currc += 1
            cp += l
        if currc > maxc:
            maxc =  currc
    return maxc

persons = []
strsn = {}
seq = ""

with open(argv[1], "r") as seqf:
    seq = seqf.read()
    seq.replace("\n", "")

dnaf = open(argv[0], "r")
dr = csv.dictReader(dnaf)
r = csv.reader(dnaf)
strs = next(r)[1 :]
for i in dr:
    persons.append(i)
for j in strs:
    strsn[j] = maxcount(len(j), j, seq)

for k in persons:
    d = []
    for z in strs:
        if strsn[z] == k[z]:
            d.append(True)
    if d.count(True) == len(strs):
        print(k["name"])
        exit(0)
print("No match")

EDIT: I have changed the code a little bit, on the advice of @Sentox. Code:

import csv
import sys

if len(sys.argv) != 3:
    print("Usage: python dna.py data.csv sequence.txt")
    sys.exit(1)

def maxcount(l, n, main, seq):
    maxc = 0
    currc = 0
    for i in range(n):
        p = i
        while p < n and seq[p : p + l] == main:
            p += l + 1
            currc += 1
        if currc > maxc:
            maxc = currc
        currc = 0
    return maxc

persons = []
strsn = {}
seq = ""

with open(sys.argv[2], "r") as seqf:
    seq = seqf.read()
    seq.replace("\n", "")

dnaf = open(sys.argv[1], "r")
dr = csv.DictReader(dnaf)
strs = dr.fieldnames[1:]
for i in dr:
    persons.append(i)
for j in strs:
    strsn[j] = maxcount(len(j), len(seq), j, seq)

for k in persons:
    d = []
    for z in strs:
        if strsn[z] == int(k[z]):
            d.append(True)
    if len(d) == len(strsn):
        print(k["name"])
        exit(0)
print("No match")

Answer 1

Some final tips:

1. != 'name': is unnecessary because the fieldnames[1:] already drops 'name'
2. strsn[z] == k[z] will never be true, because the data is read in from the CSV file as strings, while your sequence count is an integer. There's several ways to deal with this, but the most direct is to cast: int(k[z])
3. Your core issue is that your algorithm to find the longest sequences doesn't currently work. You want to find the longest run of main, but you don't do anything with main except calculate its length (which is already passed to the function as n).

Answer 2

Your code should most definitely be printing errors, not just nothing.

Your most pressing problem is that your indices for argv are wrong (you're trying to open the wrong parameters for the files you want). Once you sort that you can start debugging your code properly.

Answer 3

It can not print anything when your code does not even compile... First 2 bugs found:

1. dr = csv.dictReader(dnaf)

should be dr = csv.DictReader(dnaf)

2. argv[]

would be just an ordinary list, which is not defined in your case. In C, you would call int main( int argc, char *argv[] ) and it works just because compiler does it for you and main() function has its special meaning in C, however in Python you need not main() function for the program to run thus you need to obtain the command line arguments somehow. There is sys module to help you out and you can get them with sys.argv not only argv. You can also type from sys import argv but I prefer import sys and later explicitly use sys.argv so you know what you're working with...

Read Tracebacks errors, use https://docs.python.org/3/library/...

You may find useful regular expressions.

CSV module documentation

sys.argv documentation