获取没有 AttributeError 的类成员的值

Question

See my example

class MyClass1:
    name = 'A'
class MyClass2:
    foo = MyClass1()

obj1 = MyClass2()

Below code will result AttributeError if obj1 or foo is False .

print obj1.foo.name

So I write following

if obj1:
    if obj1.foo:
        if obj1.foo.name:
            print obj1.foo.name

What is the best way? Can I avoid the repeating words in my code ?

Answer 1

You can use try/except syntax to catch the exception.

try:
    print obj1.foo.name
except AttributeError:
    # do something

Answer 2

Your code could be simplified to two lines:

if obj1 and obj1.foo and obj1.foo.name:
    print obj1.foo.name

It checks conditions one-by-one, and if any condition of all joined by and is falsy the whole ... and ... and ... condition becomes falsy and doesn't check inner conditions further.

Answer 3

The pythonic way to resolve this is by using try/execept

try:
   name = obj1.foo.name
except AttributeError:
    # raise error or pass