Merge 2 lines with delimiter

[Buddhism]

Try to use code tags and not images with code,look at BBCode.
In my example i am running the last part in interactive shell has >>>.
Now you have put all in one function and that will not work as i have written it.
Here a example running as a script,see that need print() when running as a script.

def line_concat(lst):
    temp = zip(lst[::2], lst[::-2])
    return [':'.join(i) for i in temp]

def file_read(file_in):
    with open(file_in) as f:
        lst = [line.strip() for line in f if not line.isspace()]
        return lst

if __name__ == '__main__':
    file_in = 'xy.txt'
    lst = file_read(file_in)
    print(lst) # Test file read
    for line in line_concat(lst):
        print(line) 

Output:
['xxx.xxx.xx.xx', 'yyyy', 'xxx.xxx.xx.xx', 'yyyy']
xxx.xxx.xx.xx:yyyy
xxx.xxx.xx.xx:yyyy

xy.txt that i use to test with is:

Output:
xxx.xxx.xx.xx
yyyy






xxx.xxx.xx.xx
yyyy

Here is what I've got. The file, when I open it, is unchanged from before I added the code.
Thank you for the help so far, this stuff can just get confusing

Heres the code now:

def line_concat(lst):
    temp = zip(lst[::2], lst[::-2])
    return [':'.join(i) for i in temp]

def file_read(file_in):
    with open(file_in) as f:
        lst = [line.strip() for line in f if not line.isspace()]
        return lst



if __name__ == '__main__':
    with open("ScrapedProxys.txt","w+") as t:
        t.close()
    main()
    file_in = "ScrapedProxys.txt"
    lst = file_read(file_in)
    for line in line_concat(lst):
        f.write(line)


Clear()

input("Press Enter to Exit")

The

with open("ScrapedProxys.txt","w+") as t:

is to create the file on start