我无法使用if语句评估字典中的值。
I'm having trouble evaluating values from a dictionary using if statements.
给定以下字典,我从数据框导入(如果重要):
Given the following dictionary, which I imported from a dataframe (in case it matters):
>>> pnl[company] 29: Active Credit Date Debit Strike Type 0 1 0 2013-01-08 2.3265 21.15 Put 1 0 0 2012-11-26 40 80 Put 2 0 0 2012-11-26 400 80 Put我试图评估以下声明以建立最后一个值的值有效:
I tried to evaluate the following statment to establish the value of the last value of Active:
if pnl[company].tail(1)['Active']==1: print 'yay'但是,我遇到以下错误消息:
However,I was confronted by the following error message:
Traceback (most recent call last): File "<pyshell#69>", line 1, in <module> if pnl[company].tail(1)['Active']==1: File "/usr/lib/python2.7/dist-packages/pandas/core/generic.py", line 676, in __nonzero__ .format(self.__class__.__name__)) ValueError: The truth value of a Series is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all().这令我感到惊讶,因为我可以使用上面的命令显示我想要的值而没有if语句:
This surprised me, given that I could display the value I wanted using the above command without the if statement:
>>> pnl[company].tail(1)['Active'] 30: 2 0 Name: Active, dtype: object鉴于该值明显为零且索引为2,我尝试了以下内容进行简短的健全性检查,发现事情没有像我预期的那样发生:
Given that the value is clearly zero and the index is 2, I tried the following for a brief sanity check and found that things weren't happening as I might have expected:
>>> if pnl[company]['Active'][2]==0: ... print 'woo-hoo' ... else: ... print 'doh' doh我的问题是:
1)这里可能会发生什么?我怀疑我在一些基本层面上误解了字典。
1) What might be going on here? I suspect I'm misunderstanding dictionaries on some fundamental level.
2)我注意到,当我调出这个字典的任何给定值时,左边的数字增加了1.这代表什么?例如:
2) I noticed that as I bring up any given value of this dictionary, the number on the left increases by 1. What does this represent? For example:
>>> pnl[company].tail(1)['Active'] 31: 2 0 Name: Active, dtype: object >>> pnl[company].tail(1)['Active'] 32: 2 0 Name: Active, dtype: object >>> pnl[company].tail(1)['Active'] 33: 2 0 Name: Active, dtype: object >>> pnl[company].tail(1)['Active'] 34: 2 0 Name: Active, dtype: object提前感谢您提供任何帮助。
Thanks in advance for any help.
推荐答案您的收益是熊猫系列对象并不能以您尝试的方式进行评估,即使它只是您需要将行更改为的单个值:
What you yield is a Pandas Series object and this cannot be evaluated in the manner you are attempting even though it is just a single value you need to change your line to:
if pnl[company].tail(1)['Active'].any()==1: print 'yay'关于第二个问题,请参阅我的评论。
With respect to your second question see my comment.
编辑
从评论和链接到你的输出,调用 any()修复了错误信息,但你的数据实际上是字符串所以比较仍然失败,您可以这样做:
From the comments and link to your output, calling any() fixed the error message but your data is actually strings so the comparison still failed, you could either do:
if pnl[company].tail(1)['Active'].any()=='1': print 'yay'要进行字符串比较,或修复数据,但它已被阅读或者生成。
To do a string comparison, or fix the data however it was read or generated.
或者执行:
pnl['Company']['Active'] = pnl['Company']['Active'].astype(int)要转换列的 dtype ,以便您的比较更正确。
To convert the dtype of the column so that your comparison is more correct.
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