我有一个 pandas 系列 df.files，它看起来像这样:
In [79]: df.files
Out[79]:
0 [{'url': 'http://www.apkmirror.com/wp-content/...
1 [{'url': 'http://www.apkmirror.com/wp-content/...
2 [{'url': 'http://www.apkmirror.com/wp-content/...
3 [{'url': 'http://www.apkmirror.com/wp-content/...
4 [{'url': 'http://www.apkmirror.com/wp-content/...
5 [{'url': 'http://www.apkmirror.com/wp-content/...
6 [{'url': 'http://www.apkmirror.com/wp-content/...
7 [{'url': 'http://www.apkmirror.com/wp-content/...
8 [{'url': 'http://www.apkmirror.com/wp-content/...
9 [{'url': 'http://www.apkmirror.com/wp-content/...
10 [{'url': 'http://www.apkmirror.com/wp-content/...
11 [{'url': 'http://www.apkmirror.com/wp-content/...
12 [{'url': 'http://www.apkmirror.com/wp-content/...
13 [{'url': 'http://www.apkmirror.com/wp-content/...
14 [{'url': 'http://www.apkmirror.com/wp-content/...
15 [{'url': 'http://www.apkmirror.com/wp-content/...
16 [{'url': 'http://www.apkmirror.com/wp-content/...
17 [{'url': 'http://www.apkmirror.com/wp-content/...
18 [{'url': 'http://www.apkmirror.com/wp-content/...
19 [{'url': 'http://www.apkmirror.com/wp-content/...
20 [{'url': 'http://www.apkmirror.com/wp-content/...
21 [{'url': 'http://www.apkmirror.com/wp-content/...
22 [{'url': 'http://www.apkmirror.com/wp-content/...
23 [{'url': 'http://www.apkmirror.com/wp-content/...
24 [{'url': 'http://www.apkmirror.com/wp-content/...
25 [{'url': 'http://www.apkmirror.com/wp-content/...
26 [{'url': 'http://www.apkmirror.com/wp-content/...
27 [{'url': 'http://www.apkmirror.com/wp-content/...
28 [{'url': 'http://www.apkmirror.com/wp-content/...
29 [{'url': 'http://www.apkmirror.com/wp-content/...
...
16487 [{'url': 'http://www.apkmirror.com/wp-content/...
16488 []
16489 [{'url': 'http://www.apkmirror.com/wp-content/...
16490 [{'url': 'http://www.apkmirror.com/wp-content/...
16491 []
16492 [{'url': 'http://www.apkmirror.com/wp-content/...
16493 [{'url': 'http://www.apkmirror.com/wp-content/...
16494 [{'url': 'http://www.apkmirror.com/wp-content/...
16495 []
16496 []
16497 []
16498 [{'url': 'http://www.apkmirror.com/wp-content/...
16499 [{'url': 'http://www.apkmirror.com/wp-content/...
16500 [{'url': 'http://www.apkmirror.com/wp-content/...
16501 [{'url': 'http://www.apkmirror.com/wp-content/...
16502 [{'url': 'http://www.apkmirror.com/wp-content/...
16503 []
16504 []
16505 []
16506 []
16507 []
16508 []
16509 []
16510 []
16511 []
16512 []
16513 []
16514 []
16515 []
16516 []
一些值是空列表，而其他值是包含单个字典的列表，其格式类似于以下内容:
In [80]: df.files.loc[0]
Out[80]:
[{'checksum': '9f6075f4c561792e48354277b46a6810',
'path': 'full/80832b9fca82ce0f58f4d23c511e5a1d657c40e8.php?id=2968',
'url': 'http://www.apkmirror.com/wp-content/themes/APKMirror/download.php?id=2968'}]
我想知道有多少 df.files 的条目实际上是空列表。但是，如果我尝试 df.files.value_counts()，我会得到一个 TypeError: unhashable type: 'list'。我该如何解决这个问题？
请您参考如下方法:
如果想使用value_counts，可以先转换成tuple :
vc = df.files.apply(tuple).value_counts()
但如果只需要空列表的长度，请使用str.len对于计数 lists，然后 sum bool 掩码的所有 True:
l = (df['files'].str.len() == 0).sum()
如果没有 NaN 的值是可能的，请使用 IanS solution :
l = (df['files'].apply(len) == 0).sum()
