f.readline() != '0' even if reading a line containing only 0

Question

I do not have trouble setting variables in the program with the var = f.readline() function, but I am having trouble with the if statement when it comes to reading out of a text file. I am trying to see if a 0 is in a text file and every time I use the if f.readline() == '0': it acts as if it does not equal 0.

Example of my script below:

f = open("file.txt","r")

myvar = f.readline()
f.close



if myvar == "0":
    print "The variable is 0"
    raw_input("Press enter to continue")
else:
    print "The variable is not 0"
    raw_input("Press enter to continue")

My code would come out as The variable is not 0

Why is this? And how can I use an if statement with the readline function?

Answer 1

The readline method does not remove trailing newlines from lines. You need to do this manually:

myvar = f.readline().rstrip()

Otherwise, myvar will be equal to "0\\n" , which is not equal to "0" .

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Also, you forgot to close the file by calling the close method:

f.close() # Notice the parenthesis

Of course, using a with-statement would be better:

with open("file.txt") as f:
    myvar = f.readline().rstrip()

with will automatically close the file when control leaves its code block.