如何为Pandas DataFrame添加MergeName列：按ShortName规则填充

需求：为Pandas DataFrame添加名为MergeName的列，该列默认取ShortName列文本值；若ShortName为None，则取Plaintiffs列的值。

现有DataFrame数据如下：

Plaintiffs Gender ShortName
0           None   None      None
1           None   None      None
2    Donald Duck      M      None
3   Minnie Mouse      F    Minnie
4           None   None      None
5       John Doe      M       Doe
6           None   None      None
7           None   None      None
8           None   None      None
9           None   None      None
10          None   None      None

尝试过以下代码均未成功，常出现MergeName列仅填充else分支数据（含None值）的问题：

• 代码1：

PlaintiffsTbl['MergeName'] = np.where(PlaintiffsTbl['ShortName'] is None, PlaintiffsTbl['Plaintiffs'],  PlaintiffsTbl['ShortName'])

• 代码2：

PlaintiffsTbl['MergeName'] = PlaintiffsTbl['ShortName']
PlaintiffsTbl.loc[PlaintiffsTbl['MergeName'] == None, 'MergeName'] = PlaintiffsTbl['Plaintiffs']

• 代码3：

PlaintiffsTbl['MergeName'] = [PlaintiffsTbl['Plaintiffs'] if PlaintiffsTbl['ShortName'] is None else PlaintiffsTbl['ShortName']]

感谢Amir Hossein Shahdaei提供的可行代码：

PlaintiffsTbl['MergeName'] = PlaintiffsTbl['ShortName']
PlaintiffsTbl['MergeName'] = PlaintiffsTbl['MergeName'].fillna(PlaintiffsTbl['Plaintiffs'])

内容的提问来源于stack exchange，提问作者Rycliff