python - 如何在 pandas 中运行 for 循环

Question

我正在做 coursera 类(class)，想要使用 for 循环创建各种数据帧，其想法是创建一个列表，然后将每个 df 添加到列表中。但是，下面返回错误:

File "<ipython-input-10-2863e455a5c5>", line 7
    array.append(county_df.where(county_df['STNAME']=state))
                                ^
SyntaxError: keyword can't be an expression

<小时/>

census_df = pd.read_csv('census.csv')
county_df=census_df[census_df['SUMLEV'] == 50]
county_df.head()
county_df['STNAME'].unique()
list = []
print type(list)
for state in county_df['STNAME'].unique():
    array.append(county_df.where(county_df['STNAME']=state))

print (list)

Answer 1

在 pandas 中我们通常这样做..

l=[]

for _, df1 in county_df.groupby('STNAME'):
    l.append(df1)

您的代码错误

county_df['STNAME']=州)

应该是

county_df['STNAME']==州)

根据我的理解

county_df.loc[county_df['STNAME']==state,:]