python - Error in the coding : TypeError : list indices must be integer, not str -

code importing file, working perfectly.

but, there problem in line try import csv file, column called 'account key', returning typeerror above.

import file_import fi 

function collectively finding data necessary csv file.

def unique_students(csv_file):     unique_students_list = set()     information in csv_file:         unique_students_list.add(csv_file["account_key"])     return len(unique_students_list)  #enrollment_num_rows = len(fi.enrollments)   #engagement_num_rows = len(fi.daily_engagement)            #submission_num_rows = len(fi.project_submissions)      #enrollment_num_unique_students = unique_students(fi.enrollments) #engagement_num_unique_students = unique_students(fi.daily_engagement) #submission_num_unique_students = unique_students(fi.project_submissions) 

csv_file["account_key"]

lists expect numeric index. far know, dictionaries accept string indices.

i'm not entirely sure supposed do; think logic flawed. bind information in for loop, never use it. if list did accept string index, populate set same information on , on since for loop body remains same same every loop. work if expecting csv_file custom container type had side effects when indexed (like advancing internal counter).