pandas 在数据框上的比较 [英] Pandas boolean comparisson on dataframe
问题描述
在对数据框中的单个元素进行比较时出现错误,但是我不明白为什么.
I am getting the error when I make a comparison on a single element in a dataframe, but I don't understand why.
我有一个数据框df,其中包含许多客户的时间序列数据,其中有一些空值:
I have a dataframe df with timeseries data for a number of customers, with some null values within it:
df.head()
8143511 8145987 8145997 8146001 8146235 8147611 \
2012-07-01 00:00:00 NaN NaN NaN NaN NaN NaN
2012-07-01 00:30:00 0.089 NaN 0.281 0.126 0.190 0.500
2012-07-01 01:00:00 0.090 NaN 0.323 0.141 0.135 0.453
2012-07-01 01:30:00 0.061 NaN 0.278 0.097 0.093 0.424
2012-07-01 02:00:00 0.052 NaN 0.278 0.158 0.170 0.462
在我的脚本中,该行
if pd.isnull(df[[customer_ID]].loc[ts]):
产生错误:
In my script, the line
if pd.isnull(df[[customer_ID]].loc[ts]):
generates an error:
ValueError: The truth value of a Series is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all().
但是,如果我在脚本行上放置一个断点,并且在脚本停止时我将其输入到控制台中:
However, if I put a breakpoint on the line of script, and when the script stops I type this into the console:
pd.isnull(df[[customer_ID]].loc[ts])
输出为:
8143511 True
Name: 2012-07-01 00:00:00, dtype: bool
如果我允许脚本从这一点继续执行,则会立即生成错误.
If I allow the script to continue from that point, the error is generated immediately.
如果布尔表达式可以求值并且具有值True
,为什么它在if表达式中生成错误?这对我来说毫无意义.
If the boolean expression can be evaluated and has the value True
, why does it generate an error in the if expression? This makes no sense to me.
推荐答案
第二组[]
返回的序列是我误认为单个值的序列.最简单的解决方案是删除[]
:
The second set of []
was returning a series which I mistook for a single value. The simplest solution is to remove []
:
if pd.isnull(df[customer_ID].loc[ts]):
pass
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