Pandas DataFrame 取一行数据会得到Series的方法

lista = [1, 3, 7,4,0]
listb = [3, 3, 4,4,5]
listc = [3, 3, 4,4,6]
df1 = pd.DataFrame({'col1':lista,'col2':listb,'colb':listc})
print(df1)
print(df1.loc[0,:])
print(type(df1.loc[0,:]))

df2=df1.loc[0,:].to_frame()
print(df2)