在python字典中检查元素是否存在且是否为真的正确方法是什么？

Question

someDict = {'foo': True}
if 'foo' in someDict and someDict['foo']:
    print 'success'

Following code works fine. I'm just wondering if there is a better/shorter way of checking if key exists and its value is true.

Answer 1

someDict.get('foo')

This will return None if foo is not in someDict , otherwise it will return the value found. You can optionally pass a second argument which will be the value returned if it does not exist.

Answer 2

Nope. If you're doing this a lot, you may want to write a function to do it, though.

def ExistsTrue(d, name):
    return name in d and bool(d[name])
# usage
ExistsTrue(someDict, 'foo')

I put the bool cast in there so the function only returns True or False .