Python…sys.argv中的“ If false”：这是什么意思？

Question

I've seen this line in a python script, but I don't understand it. What does it mean?

if False or '--epson' in sys.argv:

Answer 1

Python doesn't have multi-line comments, so a hack some programmers use is to put an if False: in front of a block of code they want to disable for testing. To re-enable the block, they'd change it back to "True."

In your case, this was probably already an if statement, so they set it up like this so they could disable the entire block:

print "Hello world!"
if False: # or "--epson" in sys.argv
    print "Do something fancy with the --epson flag."
    print "Disable me if you're testing!"
    print "And me."
    print "Whoops, me too. Wow, that's a lot of single-line comments."
print "That's it, goodbye."

This is generally a bad practice because it isn't immediately obvious that this block is disabled. It's preferable to use an editor that makes it easy to comment/uncomment multiple lines at once.

Answer 2

if A or B

in this case A = False ... which will always be False

and B = "--epson" in sys.argv which will be True IFF --epson is in sys.argv

...you could rewrite this as

if "--epson" in sys.argv: