How to read a text file into a string variable and strip 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()

You can read from a file in one line:

text = open('very_Important.txt', 'r').read()

Please note that this does not close the file explicitly. To do so, you would use:

text = open('very_Important.txt', 'r').read()
# any other file operations
text.close()

CPython will close the file when it exits as part of the garbage collection. But other Python implementations won’t, so explicitly closing is important.

To write portable code, it is better to use with or close the file explicitly. Short is not always better. See Is explicitly closing files important?

The idiomatic method is to use with and as which has been implemented since Python 2.5. All modern versions of Python support this.

with open('very_Important.txt', 'r') as text:
    very_important_text = text.read()
    # any other file operations
# automatically closes and cleans up file handling outside of indent
# very_important_text contains the file text in a string and can be used
print(very_important_text)

To join all lines into a string and remove new lines, I normally use:

with open('t.txt') as f:
  s = " ".join([l.rstrip("\n") for l in f]) 

Use:

with open("data.txt") as myfile:
    data = "".join(line.rstrip() for line in myfile)

join() will join a list of strings, and rstrip() without any arguments will trim whitespace, including newlines, from the end of strings.