python - 如何从 Pandas 数据框中检索列值并检查条件

Question

Dataframe 列 Class 由 2 个值 0 和 1 组成。我想计算 Class 0 有多少行以及 Class 1 有多少行。我编写了这样的代码

genuine_count=0
fraud_count=0
if credit_card_df['Class'] == 1:
    fraud_count +=1
else:
    genuine_count +=1
print "Genuine transactions"+genuine_count
print "Fraud transactions"+fraud_count

我收到此错误

ValueError                                Traceback (most recent call last)
<ipython-input-12-2e8ec920b69d> in <module>()
      1 genuine_count=0
      2 fraud_count=0
----> 3 if credit_card_df['Class'] == 1:
      4     fraud_count +=1
      5 else:

C:\Users\JAYASHREE\Anaconda2\lib\site-packages\pandas\core\generic.pyc in __nonzero__(self)
    890         raise ValueError("The truth value of a {0} is ambiguous. "
    891                          "Use a.empty, a.bool(), a.item(), a.any() or a.all()."
--> 892                          .format(self.__class__.__name__))
    893 
    894     __bool__ = __nonzero__

ValueError: The truth value of a Series is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all().

请帮我解决。谢谢

Answer 1

谢天谢地，pandas 已经为您编写了此内容:

credit_card_df['Class'].value_counts()

或者，如果您想以自己的格式打印:

genuine_count, fraud_count = credit_card_df['Class'].value_counts(sort=True)

print "Genuine transactions"+genuine_count
print "Fraud transactions"+fraud_count