熊猫：字符串匹配的AND OR问题

Question

我要筛选几个部门-然后，我需要显示不匹配的数字。

• Dept1
• Dept2
• Dept3

查找单个部门提供的程序数量：

cond = events['Event Type'].str.contains('Outreach') & (events['Presenter'].str.contains('[Dd]ept1', regex=True))
dpta = events[cond]
dpta_att = dpta['Attendance'].sum()
dpta_num = len(dpta.index)

从理论上讲，以下内容似乎会给我提供属于上述任何部门的剩余程序 not ：

pattern = '[Dd]ept1|[Dd]ept2|[Dd]ept3'
leftover_cond = events['Event Type'].str.contains('Outreach') & (events['Presenter'].str.contains(pattern, case=False, regex=True)==False | events['Presenter'].isnull())
leftover_outreach = events[leftover_cond]
leftover_outreach_att = leftover_outreach['Attendance'].sum()
leftover_outreach_num = len(leftover_outreach.index)

我得到的数字比预期的少得多。

数据：

Location          Attendance        Event Type               Presenter
HR Office         10                Outreach                 DeptA
Board Room        5                 Admin                    Billy
Offsite           103               Outreach                 DeptB