Write and read a list from file

Question

This is a slightly weird request but I am looking for a way to write a list to file and then read it back some other time.

I have no way to remake the lists so that they are correctly formed/formatted as the example below shows.

My lists have data like the following:

test
data
here
this
is one
group :)

test
data
here
this
is another
group :)

Answer 1

As long as your file has consistent formatting (i.e. line-breaks), this is easy with just basic file IO and string operations:

with open('my_file.txt', 'rU') as in_file:
    data = in_file.read().split('\n')

That will store your data file as a list of items, one per line. To then put it into a file, you would do the opposite:

with open('new_file.txt', 'w') as out_file:
    out_file.write('\n'.join(data)) # This will create a string with all of the items in data separated by new-line characters

Hopefully that fits what you're looking for.

Answer 2

Let's define a list first:

lst=[1,2,3]

You can directly write your list to a file:

f=open("filename.txt","w")
f.write(str(lst))
f.close()

To read your list from text file first you read the file and store in a variable:

f=open("filename.txt","r")
lst=f.read()
f.close()

The type of variable lst is of course string. You can convert this string into array using eval function.

lst=eval(lst)