How can I read a text file into a string variable and strip newlines?

I have a text file that looks like:

ABC
DEF

How can I read the file into a single-line string without newlines, in this case creating a string 'ABCDEF'?

For reading the file into a list of lines, but removing the trailing newline character from each line, see How to read a file without newlines?.

You could use:

with open('data.txt', 'r') as file:
    data = file.read().replace('\n', '')

Or if the file content is guaranteed to be one line:

with open('data.txt', 'r') as file:
    data = file.read().rstrip()

Stack Overflow Q#8369219, score: 1978