向 pandas 数据框添加空值 [英] Adding null values to a pandas dataframe
问题描述
我有一个用于创建JSON的熊猫数据框,而JSON又用于显示高位图表.
I have a pandas dataframe that is used to create a JSON which in turn is used to display a highcharts chart.
熊猫数据框:
Date colA colB
12-Sep-14 20 40
13-Sep-14 50 10
14-Sep-14 12 -20
15-Sep-14 74 43
是否可以将一些colA和colB值更改为null.原因是我最终需要一个看起来像这样的JSON:
Is there a way to change some of the colA and colB values to null. The reason for this is that I ultimately need a JSON that looks something like this:
[
[12-Sep-14, 20, 40],
[13-Sep-14, null, null],
[14-Sep-14, 12, -20],
[15-Sep-14, 74, 43]
]
原因是我需要一个高图图表,其中某些绘图点为空白.为此,请指定日期,后跟null.
The reason for this is that I require a highcharts chart where certain plot points are blank. To do this, you specify the date followed by null.
因此,我需要以某种方式更新pandas数据框中的某些值,以便一旦我使用.to_json()将其转换为JSON,则json将包含上述示例中指定的空值.
So I need to somehow update certain values in the pandas dataframe so that once I convert it to a JSON using .to_json() then the json will contain the specified null values as per the example above.
谢谢您的建议.
推荐答案
这项工作有效吗?
import pandas as pd
# Read in data frame from clipboard
df = pd.read_clipboard()
df = df.replace(df.iloc[1][1:],'null')
Date colA colB
0 12-Sep-14 20 40
1 13-Sep-14 null null
2 14-Sep-14 12 -20
3 15-Sep-14 74 43
在这里,df.iloc [1]可以访问第1行
Here, df.iloc[1] gives access to row 1
最后,
df.to_json(orient='values').replace("\"","")
提供不带"的json
gives json without the ""
[[12-Sep-14,20,40],[13-Sep-14,null,null],[14-Sep-14,12,-20],[15-Sep-14,74,43]]
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