CODEWITHSUNDEEP
pythonlistfilenested
Anuj Vikal
Anuj Vikal

Reputation: 81

How to read a file to a list of lists?

I want to create a list of lists from a file that contains the following data:

101 Rahul
102 Julie
103 Helena
104 Kally

CODE

lis = []

with open("student_details.txt" , "r+") as f:    
    for i in range(1,3,1):
        for data in f.read().split():
            lis.append(data)
print(lis)

Output I Want

[[101,Rahul] ,[102,Julie] ,[103,Helena] ,[104,Kally]]

Output I m getting

['101', 'Rahul', '102', 'Julie', '103', 'Helena', '104', 'Kally']

Upvotes: 4

Views: 1073

Answers (5)

OddNorg
OddNorg

Reputation: 898

You can split by lines: 

lis = []

with open("student_details.txt" , "r+") as f:    
    for line in f:
       data = line.split()
       lis.append(data)
print(lis)

Result :

[['101', 'Rahul'], ['102', 'Julie'], ['103', 'Helena'], ['104', 'Kally']]

Or in a more compact way :

with open("student_details.txt" , "r+") as f:    
    lis = [line.split() for line in f]
print(lis)

Result :

[['101', 'Rahul'], ['102', 'Julie'], ['103', 'Helena'], ['104', 'Kally']]

Upvotes: 1

goddar
goddar

Reputation: 131

You could try this alternative too. I'm using splitlines() method.

data = []
f = open('student_details.txt', 'r')
for line in f.read().splitlines():
    data.append([line])
print(data)

Upvotes: 0

Mohd
Mohd

Reputation: 5613

Easiest way is to do it by list comprehension as the following:

with open("student_details.txt" , "r+") as f:
    lis = [line.split() for line in f]

or if you want to loop you can loop through the file without reading it:

with open("student_details.txt" , "r+") as f:    
    lis = []
    for line in f:
        lis.append(line.split())

Upvotes: 2

Baldrickk
Baldrickk

Reputation: 4409

Your code:

lis = []

with open("student_details.txt" , "r+") as f:    
    for i in range(1,3,1):
        for data in f.read().split():
            lis.append(data)
print(lis)

Note the two for loops, what you are doing is looping through each line, then through each item on that line. You are then pushing each item individually into your list lis. To get the output you want, you want to be pushing a list of the two items on each line into your list. You are actually already generating this list of items with f.read().split(), so you just need to append this. This leaves you with the following:

lis = []

with open("student_details.txt" , "r+") as f:    
    for i in range(1,3,1):
        #no second loop here
        data = f.read().split()
        lis.append(data)
print(lis)

This still doesn't give us the correct answer, the loop is the problem here, we can fix this by just reading each line ideomatically, without specifying any ranges:

lis = []

with open("student_details.txt" , "r+") as f:    
    for line in f:
        #no second loop here
        data = line.split()
        lis.append(data)
print(lis)

Upvotes: 1

Jean-François Fabre
Jean-François Fabre

Reputation: 140287

You could read line by line iterating on the handle or using readlines(), splitting each line, appending each result, etc... Fixing your code would require to remove the range loop which just reads the file 3 times (but only effectively reads once the first time), and append the splitted items of the lines, using a list comprehension to be more pythonic:

with open("student_details.txt" , "r+") as f:    
     lis = [line.split() for line in f]

note that the cool thing about line.split() (without parameters) is that it gets rid of the line terminator(s) automatically.

but you can make it simpler: csv module does all the parsing for you:

import csv
with open("student_details.txt" , "r") as f:
   cr = csv.reader(f,delimiter=" ")
   # iterate on rows and generate list of lists:
   result = list(cr)

Upvotes: 3

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