类型错误：int64 类型的 Object 不是 JSON 可序列化 | pandas 聚合函数和 json.dumps() 错误

Question

Pandas aggregation functions return TypeError: Object of type int64 is not JSON serializable.

Here is the dataframe:

d = {'col1': [1, 2], 'col2': [3, 4]}
df = pd.DataFrame(data=d)
df
Out[47]: 
   col1  col2
0     1     3
1     2     4

Here is how I am aggregating the column:

sum_col = df.col1.sum()
sum_col
Out[49]: 3

But as soon as I do json.dumps() it gives a type error:

data = json.dumps(sum_col)
data
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-50-5d4b966e64cc> in <module>
----> 1 data = json.dumps(sum_col)
      2 data
TypeError: Object of type int64 is not JSON serializable

Answer 1

I resolved this one.

Pandas aggregation functions (like sum, count and mean) returns a NumPy int64 type number, not a Python integer. Although it looks exactly like a python integer.

d = {'col1': [1, 2], 'col2': [3, 4]}
df = pd.DataFrame(data=d)
sum_col = df.col1.sum()
type(sum_col)

Out[52]: numpy.int64

This can be fixed by using python's int() function.

sum_col = int(df.col1.sum())
data = json.dumps(sum_col)
data

Out[56]: '3'