Is there a way to write a 'list of lists' to a .txt file in a certain format

Question

I have a list of lists like the one below:

alist = [['Hi', 500], ['Bye', 500.0, 100, 900, 600], ['Great', 456, 700.0, 600], ["Yay", 200, 350.0], ["Ok", 200, 300, 400.0]]

I want to write this list to a .txt file in such a way that the textfile contents look something like this, with the first string written with a space after it, and the rest of the values separated by commas:

Desired output:

Hi 500

Bye 500.0,100,900,600

Great 246,700.0,600

Yay 200,350.0

Ok 200,300,400.0

This is what I've been trying out so far:

txtfile = open("filename.txt", "w")
        for i in alist:
            txtfile.write(i[0] + " ")
            j = 1
            while j < len(i):
                txtfile.write([i][j] + ",")
            txtfile.write("\n")

However, I just keep getting the IndexError("List Index out of range") error.

Is there any way to solve this without importing any modules?

Thanks in advance :)

ferdy · Accepted Answer · 2021-11-04 08:50:12Z

1

Other method.

alist = [['Hi', 500], ['Bye', 500.0, 100, 900, 600], ['Great', 456, 700.0, 600], ["Yay", 200, 350.0], ["Ok", 200, 300, 400.0]]

fn = "filename.txt"
mode = "w"
with open(fn, mode) as h:  # file handle is auto-close
    for v in alist:
        h.write(v[0] + " ")
        j = 1
        while j < len(v):
            if len(v) - 1 == j:
                h.write(str(v[j]))  # don't write a comma if this is the last item in the list
            else:
                h.write(str(v[j]) + ",")
            j += 1  # increment j to visit each item in the list
        h.write("\n")

Output

Hi 500
Bye 500.0,100,900,600
Great 456,700.0,600
Yay 200,350.0
Ok 200,300,400.0

answered Nov 4, 2021 at 8:50

ferdy

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Comments

vtasca · Accepted Answer · 2021-11-04 08:28:46Z

1

This is quick, easy and works without any imports:

str(alist).replace('],', '\n').replace('[', '').replace(']', '').replace("'", '')

Giving you:

Hi, 500
 Bye, 500.0, 100, 900, 600
 Great, 456, 700.0, 600
 Yay, 200, 350.0
 Ok, 200, 300, 400.0

Which you can write to disk as:

alist = str(alist).replace('],', '\n').replace('[', '').replace(']', '').replace("'", '')
with open('filename.txt', 'w') as f:
    f.write(alist)

answered Nov 4, 2021 at 8:28

vtasca

1,78014 silver badges18 bronze badges

1 Comment

Pranav Sundaram Over a year ago

Hi, in the output, I don't want a comma after the string, just a space. And in between the values, I only want a comma, no spaces. That is what is making me struggle with this problem

iamjing66 · Accepted Answer · 2021-11-04 08:47:29Z

1

maybe you can try this code:

to use list() 、map() and str.join()


alist = [['Hi', 500], ['Bye', 500.0, 100, 900, 600], ['Great', 456, 700.0, 600], ["Yay", 200, 350.0], ["Ok", 200, 300, 400.0]]

t = open("a.txt", "w")
for i in alist:
    t.writelines(i[0] + " " + ",".join(list(map(str, i[1:])))+"\n")

# if you want to do it without map()
# you can use list comprehension
# ","join([str(j) for j in i[1:])

and outputfile

Hi 500
Bye 500.0,100,900,600
Great 456,700.0,600
Yay 200,350.0
Ok 200,300,400.0

edited Nov 4, 2021 at 8:47

answered Nov 4, 2021 at 8:33

iamjing66

616 bronze badges

5 Comments

Pranav Sundaram Over a year ago

Hi, thank you for this. Is there a way to this without the map function.

iamjing66 Over a year ago

@Pranav-sundaram you can use "."join([str(j) for j in i[1:]) to replace.

iamjing66 Over a year ago

@Timus Sry, my bad. Forgot to remove it. :p

Pranav Sundaram Over a year ago

Oh, ok. Thank you so much.

Timus Over a year ago

Just add your (corrected) comment in the answer and then you have one :)

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