Gather CSV file(s) into XLSX Sheets

attendance_sheet_maker.py

import csv
import pandas as pd
from collections import defaultdict

header = None
created_sheets = defaultdict(list)
lc = None

with open('INPUT.csv') as f:
    reader = csv.reader(f)
    lines = list(reader)
    lc = len(lines) - 1

    header = lines[0][1:]
    for line in lines[1:]:
        sheet = line[0]

        if sheet not in created_sheets:
            created_sheets[sheet].append(header)

        created_sheets[sheet].append(line[1:])

writer = pd.ExcelWriter('OUTPUT.xlsx')
lco = 0

for key, data in created_sheets.items():
    df = pd.DataFrame(data)
    df.to_excel(writer, key, index=False, header=False)
    lco += len(data) - 1

assert(lc==lco)

writer.close()