python - how to detect empty / null value in list which may contain numeric or string?

Question

I have list containing multiple dictionary objects. I want to detect when there is no value in a specific key-value pair. When the value exists it is numeric. When the value does not exist, it appears to be is an empty string (judging from the Stack Data).

Initially I tried:

for dictionary_item in row_list:
    if dictionary_item['targetkey'] == '':
        #do stuff

This throws an "unsupported operand type" error when it encounters a number.

The value in the key-value pair may be either a number or an empty string. What is a good test expression for this scenario?

Answer 1

我个人会使用isinstance：

if isinstance(dictionary_item['targetkey'], float):

即使数字是0.0，这也将起作用，False在 Python 中计算为 。

请看下面的演示：

>>> bool(0.0)
False
>>> isinstance(0.0, float)
True
>>> isinstance(10.0, float)
True
>>> isinstance('', float)
False
>>>

Answer 2

试试这个，只要字典中的值不包括零，它就可以工作：

if dictionary_item['targetkey']:
    # do stuff

以上将检查是否dictionary_item['targetkey']为非空、非空和非零。如果零是字典中的有效值，则执行以下操作：

if dictionary_item['targetkey'] or dictionary_item['targetkey'] == 0:
    # do stuff