Python-None参数

我有一个具有4个参数的函数：

   def uploadDatabase(user,filter1,filter2, name):
        """uploads playlists to database

        if a playlist satisfying both filters is not long enough,
        we pick a playlist based on one single filter"""

        playlist_filter1 = [x['track'] for x in filter1]
        playlist_filter2 = [x['track'] for x in filter2]
        playlist_both_filters = [x['track'] for x in filter2 if x['track'] in [y['track'] for y in filter1]]

       #create an empty dict for user as key
       double_filter = {str(user):{}}
       single_filter1 = {str(user):{}}
       single_filter2 = {str(user):{}}
       #set initial playback number for each track
       count = 1
       #set counts to tracks
       double_filter[str(user)] = dict(zip(playlist_both_filters, [count for i in playlist_both_filters]))
       db_double = double_filter 
       #set counts to tracks
       single_filter1[str(user)] = dict(zip(playlist_filter1, [count for i in playlist_filter1]))
       db_single1 = single_filter1 
       (...)

但是，有时无法通过

filter2

：

uploadDatabase(user,energy_playlist, None, 'my playlist')

---

如何修复

uploadDatabase（）

并告诉它忽略分配给变量

playlist\u filter2

和

double\u filter

的

None-Type

，因为两者都需要有效的

列表

？

您可以通过以下操作将

None

类型转换为两个过滤器的有效空列表：

playlist_filter1 = [x['track'] for x in filter1] if filter1 is not None else []
playlist_filter2 = [x['track'] for x in filter2] if filter2 is not None else []

而不是：

playlist_filter1 = [x['track'] for x in filter1]
playlist_filter2 = [x['track'] for x in filter2]

---

您可以通过执行以下操作将两个筛选器的

None

类型转换为有效的空列表：

playlist_filter1 = [x['track'] for x in filter1] if filter1 is not None else []
playlist_filter2 = [x['track'] for x in filter2] if filter2 is not None else []

而不是：

playlist_filter1 = [x['track'] for x in filter1]
playlist_filter2 = [x['track'] for x in filter2]

---

如果我理解正确，您需要检查参数filter2是否被传递

要做到这一点很简单，您实际上给它一个默认值为

None

，然后在代码中检查参数是否为

None

示例代码

---

当您使用函数时，您可以传递filter2，它将覆盖默认的

None

值，或者不传递它，它将是

None

，如果我理解正确，您需要检查参数filter2是否被传递

要做到这一点很简单，您实际上给它一个默认值为

None

，然后在代码中检查参数是否为

None

示例代码

---

当您使用该功能时，您可以通过filter2，它将覆盖默认的

None

值，或者只是不通过它，它将是

None

请更新您的答案，以便它修复播放列表\u两个过滤器=[x['track']对于过滤器2中的x，如果[y['track']中的x['track']对于过滤器1中的y]，同样使用

如果条件

，请更新您的答案，以便它也使用

如果条件

，也可以使用

如果条件

，则在过滤器2中为x修复

播放列表(两个过滤器=[x['track']