lists and reading from file comma separated elements

Question

Here is my code

#course registration
list_courses=[]
for line in open("courses.txt",'r').readlines():
    list_courses.append(line.strip())
print ("Gathering course information from file: \n",list_courses)
close("courses.txt")
list_student=[]
for line in open("students.txt",'r').readlines():
    list_student.append(line.strip())
print("Here is student info: \n",list_student)
close("students.txt")

this is giving me errors when I try to close the files. How do I close, I am basically reading contents of file and storing them in a list. Now later on want to close the open files.There I get error.

I edited the code as per suggestions below. The new code is

list_courses=[]
with open("courses.txt",'r') as myfile1:
      list_courses=myfile1.readlines()
      list_courses=[x.strip() for x in list_courses]

print ("Gathering course information from file: \n",list_courses)

list_student=[]
with open("students.txt",'r') as myfile1:
      list_student=myfile1.readlines()
      list_student=[x.strip() for x in list_student]

print("Here is student info: \n",list_student)

The information in courses.txt is

cs101,C programming
cs102,Digital logic and design
cs103,Electrical engineering
cs231,IT networks
cs232,IT Workshop
cs233,IT programming
cs301,Compilers and automata
cs302,Operating Systems
cs303,Networks
cs401,Game Theory
cs402,Systems Programming
cs403,Automata
ec101,Digitization
ec102,Analog cicuit design
ec103,IP Telephony
ec201,Wireless Network
ec202,Microwave engineering
ec203,Antenna
ec301,Maths2
ec302,Theory of Circuits
ec303,PCB design
ec401,PLC programming
ec402,Scada
ec403,VLSI

When I run the code I get output

Gathering course information from file: 

     ['cs101,C programming', 'cs102,Digital logic and design', 'cs103,Electrical engineering', 'cs231,IT networks', 'cs232,IT Workshop', 'cs233,IT programming', 'cs301,Compilers and automata', 'cs302,Operating Systems', 'cs303,Networks', 'cs401,Game Theory', 'cs402,Systems Programming', 'cs403,Automata', 'ec101,Digitization', 'ec102,Analog cicuit design', 'ec103,IP Telephony', 'ec201,Wireless Network', 'ec202,Microwave engineering', 'ec203,Antenna', 'ec301,Maths2', 'ec302,Theory of Circuits', 'ec303,PCB design', 'ec401,PLC programming', 'ec402,Scada', 'ec403,VLSI']

Instead of it what I want is the input cs101 from the first line of courses.txt to go in list_courses[0] and list_courses[1] to have c programming i.e. list_courses[0]=cs101 list_courses[1]=C programming

So I tried methods where programe have taken a line and read the line stored that line as an element of list but there is a comma which separates two elements in courses.txt and comma separated values should be separate list elements.

You can't do that. Use the `with` context manager, then it gets closed for you when the block exits: `with open('courses.txt', 'r') as course_file: ...`. — jonrsharpe, Aug 16 '18 at 14:27
Possible duplicate of [python close file descriptor question](https://stackoverflow.com/questions/4599980/python-close-file-descriptor-question) — Scott Mermelstein, Aug 16 '18 at 15:37

Inder · Accepted Answer · 2018-08-16T16:18:27.433

0

This will work for you:

students=[]
subject=[]
with open("students.txt","r") as f:
    for line in f.readlines():
        eachl=line.split(",")
        students.append(eachl[0])
        subject.append(eachl[1][:-1])

you will get two lists containing student names and another one with subjects:

students list will look like:

['cs101', 'cs102', 'cs103', 'cs231', 'cs232', 'cs233', 'cs301', 'cs302', 'cs303', 'cs401', 'cs402', 'cs403', 'ec101', 'ec102', 'ec103', 'ec201', 'ec202', 'ec203', 'ec301', 'ec302', 'ec303', 'ec401', 'ec402', 'ec40`3]

subjects list will look like:

['C programming', 'Digital logic and design', 'Electrical engineering', 'IT networks', 'IT Workshop', 'IT programming', 'Compilers and automata', 'Operating Systems', 'Networks', 'Game Theory', 'Systems Programming', 'Automata', 'Digitization', 'Analog cicuit design', 'IP Telephony', 'Wireless Network', 'Microwave engineering', 'Antenna', 'Maths2', 'Theory of Circuits', 'PCB design', 'PLC programming', 'Scada', 'VLSI']

edited Aug 16 '18 at 16:18

answered Aug 16 '18 at 14:31

Inder

3,711
9
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@ss321c updating my answer – Inder Aug 16 '18 at 16:18
what does `subject.append(eachl[1][:-1])` do this line is not clear to me – ss321c Aug 16 '18 at 16:31
It is doing away with the \n that exists in a the string so it's just giving everything except the last character of the string – Inder Aug 16 '18 at 16:32
you mean using[:-1] is removing \n – ss321c Aug 16 '18 at 16:38
yes @ss321c its removing \n eg if we have a string like s="abc" if i do s[:-1] we get "ab" – Inder Aug 16 '18 at 16:39
please see this question also https://stackoverflow.com/questions/51882609/combining-two-list-into-third-based-on-condition – ss321c Aug 16 '18 at 18:41

MJCS · Answer 2 · 2018-08-16T16:59:17.470

0

Why don’t you try

students = []
courses = []

open(“courses.txt”, “r”) as f
for line in f.readlines()
    a, b = line.split(“,”)
    students.append(a)
    courses.append(b[:-1])
f.close()

This will produce two lists students and courses

edited Aug 16 '18 at 16:59

answered Aug 16 '18 at 14:34

MJCS

31
1
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lists and reading from file comma separated elements

2 Answers2