只适用第一个条件

Question

我是Python的新手。我希望进行以下筛选，但只应用第一个条件，而忽略其他条件。你能告诉我我哪里错了吗？这是我的数据：

​

import pandas as pd
census_df = pd.read_csv('census.csv')
census_df.head()
census_df

val1=census_df['POPESTIMATE2015']
val2=census_df['POPESTIMATE2014']

def answer_one():

    return census_df[val1>val2 & (census_df['REGION']==1 | (census_df['REGION']==2) & (census_df['CTYNAME'].str.len=='Washington') ) ] 

answer_one()

Answer 1

我想你需要知道这个(Python运算符优先)：

**          Exponentiation (raise to the power)
~ + -       Ccomplement, unary plus and minus (method names for the last two are +@ and -@)
* / % //    Multiply, divide, modulo and floor division
+ -         Addition and subtraction
>> <<       Right and left bitwise shift
&           Bitwise 'AND'td>
^ |         Bitwise exclusive `OR' and regular `OR'
<= < > >=   Comparison operators
<> == !=    Equality operators
= %= /= //= -= += *= **=    Assignment operators
is is not   Identity operators
in not in   Membership operators
not or and  Logical operators

就你的情况而言：

census_df[(val1 > val2) & ((census_df['REGION']==1) | 
                           (census_df['REGION']==2)) & 
                           (census_df['CTYNAME']=='Washington')]

可能是你要找的？

Answer 2

在对所有条件设置parens之后，您的代码：

return census_df[(val1>val2) & ((census_df['REGION']==1) | (census_df['REGION']==2) & (census_df['CTYNAME'].str.len=='Washington') ) ] 

评估为..。

(val1>val2)按位和 (普查_df‘’REGION‘=2)按位和(census_df'CTYNAME'.str.len=='Washington')bitwise或 (普查_df‘’REGION‘=1)

请注意，您使用的是按位和(&)、按位或(\)。它们有一些不同于布尔和布尔或。