Why is "if x is none" statement not executing properly?

Question

It's obvious I'm doing something wrong, but I can't find help online as to why. I want to create an if function that prints out that the inputted file contains no data. When I run this and request an empty.txt file, it skips straight to the else: and I get

Enter name of file: empty.txt

In the terminal, instead of the printed result, I'm asking for.

 # Ask user to input file, open and and read file

userinput = input('Enter name of file: ')

userfile = open(userinput)

data = userfile.read()

#if file is empty print "x contains no data"

if data is None:
    print(userinput + ' contains no data.')
else:
    print(data)

userfile.close()

`.read()` returns a string. If the file was empty, you'd just get an empty string - rather than `None`. — jasonharper, Oct 24 '22 at 01:11
@MarkRansom the terminal returns: Enter name of file: empty.txt and a second empty line, and I'm guessing that is representative of the empty contents of my sample empty.txt file that I input. — Filth, Oct 24 '22 at 01:19

score 0 · Answer 1 · answered Oct 24 '22 at 01:22

0

 # Ask user to input file, open and and read file

userinput = input('Enter name of file: ')

userfile = open(userinput)

data = userfile.read()

#if file is empty print "x contains no data"
if len(data) == 0:
    print(userinput + ' contains no data.')
else:
    print(data)

userfile.close()

this works, because read an empty file returns an empty string "", you can check it by condition len(data) == 0

answered Oct 24 '22 at 01:22

Xi Gou

49
2

2

Actually you can just use `if not data:` because an empty string is considered False, unlike any other string. – Mark Ransom Oct 24 '22 at 01:24

Why is "if x is none" statement not executing properly?

1 Answers1