How to check if the string is empty?

Question

Does Python have something like an empty string variable where you can do:

if myString == string.empty:

Regardless, what\'s the most elegan

Answer 1

Another easy way could be to define a simple function:

def isStringEmpty(inputString):
    if len(inputString) == 0:
        return True
    else:
        return False

Answer 2

a = ''
b = '   '
a.isspace() -> False
b.isspace() -> True

Answer 3

How about this? Perhaps it's not "the most elegant", but it seems pretty complete and clear:

if (s is None) or (str(s).strip()==""): // STRING s IS "EMPTY"...

Answer 4

Responding to @1290. Sorry, no way to format blocks in comments. The None value is not an empty string in Python, and neither is (spaces). The answer from Andrew Clark is the correct one: if not myString. The answer from @rouble is application-specific and does not answer the OP's question. You will get in trouble if you adopt a peculiar definition of what is a "blank" string. In particular, the standard behavior is that str(None) produces 'None', a non-blank string.

However if you must treat None and (spaces) as "blank" strings, here is a better way:

class weirdstr(str):
    def __new__(cls, content):
        return str.__new__(cls, content if content is not None else '')
    def __nonzero__(self):
        return bool(self.strip())

Examples:

>>> normal = weirdstr('word')
>>> print normal, bool(normal)
word True

>>> spaces = weirdstr('   ')
>>> print spaces, bool(spaces)
    False

>>> blank = weirdstr('')
>>> print blank, bool(blank)
 False

>>> none = weirdstr(None)
>>> print none, bool(none)
 False

>>> if not spaces:
...     print 'This is a so-called blank string'
... 
This is a so-called blank string

Meets the @rouble requirements while not breaking the expected bool behavior of strings.

Answer 5

As prmatta posted above, but with mistake.

def isNoneOrEmptyOrBlankString (myString):
    if myString:
        if not myString.strip():
            return True
        else:
            return False
    return False

Answer 6

You may have a look at this Assigning empty value or string in Python

This is about comparing strings that are empty. So instead of testing for emptiness with not, you may test is your string is equal to empty string with "" the empty string...