Why is only the last item showing when I want to print a list from a file in python?

Question

Just a warning I am as beginner as it gets with python so I might ask for clarification with answers if it’s beyond what I’ve learned in class.

My text file is titled ‘data.txt’ and looks like this (the file ends at 80):

My code looks like this:

data = open('data.txt', 'r')

    for line in data:
        newLine = line.strip('n')
        dataList = newLine.split('n')

    #This closes the file
    data.close()
    
    print('The numbers are ', dataList)

    countNumbers = len(dataList)

    print('The count of the numbers is ', countNumbers)

When I run the program the output is:

The numbers are  ['80']

The count of the numbers is  1

So I don’t understand why I am not getting back all 3 elements of the list. Thank you.

Asked By: whatsanoven

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Source

Answer 1

The reason why you are getting the last number is because you are just saving 1 item to the dataList variable in every loop, you are not creating a list. You are overwriting it at every loop.

I am not sure what your text file looks like but it seems like there are spaces between each line, so my data.txt file literally looks like this. It has 5 lines, 3 with something and 2 blank ones in between.

Okay so here is my code,

data = open('data.txt', 'r')
dataList = [] #create empty list

for line in data:
    new = line.strip('n')
    if new: #check if there is data because when you strip a blank new line, you still get an empty string
        dataList.append(new) #append line to dataList

data.close()
print('The numbers are ', dataList)
countNumbers = len(dataList)
print('The count of the numbers is ', countNumbers)

Here is my output,

The numbers are  ['90', '100', '80']
The count of the numbers is  3

Here is an implementation with split that gives the same result. Not recommended because it’s not as efficient since we know that there is only 1 item per line. We just need to get rid of the n (new line character).

data = open('data.txt', 'r')
dataList = []

for line in data:
    new = line.split('n')[0] #select first item in array
    if new:
        dataList.append(new)

print('The numbers are ', dataList)
countNumbers = len(dataList)

print('The count of the numbers is ', countNumbers)

Answered By: anarchy

Answer 2

I did it this way:

data = open('data.txt', 'r')

dataList = []

for line in data:
    if line != "n":
        dataList.append(line.replace("n",""))
   

#This closes the file
data.close()

print('The numbers are ', dataList[:])

countNumbers = len(dataList[:])

print('The count of the numbers is ', countNumbers)

I hope it helps

Answered By: joellpaim

Answer 3

Use the read method to turn the entire file into an array of strings, then iterate through the file:

data = open('data.txt', 'r')

dataList = []
for number in data.read().split("n"):
    if number != '':
        dataList.append(int(number))

#This closes the file
data.close()

Answered By: Jack Bosco

Answer 4

You can do it just in one line, using the splitlines method like this:

data = open('data.txt', 'r')
dataList = data.read().splitlines() # Put the file line by line  in a List
dataList = list(filter(None, dataList)) # Remove all empty list elements

data.close()


print('The numbers are ', dataList)
countNumbers = len(dataList)
print('The count of the numbers is ', countNumbers)

Answered By: AziMez

Answer 5

We could give a try to my approach buddy.I certainly hope this helps, pal!

with open('data.txt') as f:
    lines_lst = [line.strip() for line in f.read().splitlines()]
    [lines_lst.remove(el) for el in lines_lst if el ==""]
        
    print('The numbers are ', lines_lst)
    print('The count of the numbers is ',  len(lines_lst))

Answered By: Alvison Hunter

Why is only the last item showing when I want to print a list from a file in python?

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