熊猫数据框合并

Question

我是熊猫新手。我正在尝试制作一个带有邮政编码，该邮政编码中的人口数字和邮政编码中的县数的数据集。

我从人口普查网站上的数据：https://www2.census.gov/geo/docs/maps-data/data/rel/zcta_county_rel_10.txt

我用下面的代码很努力，但它不工作。你能帮我弄清楚正确的代码吗？我有一个预感，错误是由于数据框或与数据类型相关的排序。但是我无法弄清楚正确的代码是否正确。请让我知道你的想法。先谢谢你！

import pandas as pd 

df = pd.read_csv("zcta_county_rel_10.txt", dtype={'ZCTA5': str, 'STATE': str, 'COUNTY': str}, usecols=['ZCTA5', 'STATE', 'COUNTY', 'ZPOP']) 

zcta_pop = df.drop_duplicates(subset={'ZCTA5', 'ZPOP'}).drop(['STATE', 'COUNTY'], 1) 

zcta_ct_county = df['ZCTA5'].value_counts() 

zcta_ct_county.columns = ['ZCTA5', 'CT_COUNTY'] 

pre_merge_1 = pd.merge(zcta_pop, zcta_ct_county, on='ZCTA5')[['ZCTA5', 'ZPOP', 'CT_COUNTY']] 

这是我的错误信息：

Traceback (most recent call last):  
File "<stdin>", line 1, in <module>  
File "/usr/local/python27/lib/python2.7/site-packages/pandas/tools/merge.py", line 58, in merge copy=copy, indicator=indicator) 
File "/usr/local/python27/lib/python2.7/site-packages/pandas/tools/merge.py", line 473, in __init__ 'type {0}'.format(type(right)))  
ValueError: can not merge DataFrame with instance of type <class 'pandas.core.series.Series'> 

SOLUTION

import pandas as pd 
df = pd.read_csv("zcta_county_rel_10.txt", dtype={'ZCTA5': str, 'STATE': str, 'COUNTY': str}, usecols=['ZCTA5', 'STATE', 'COUNTY', 'ZPOP']) 
zcta_pop = df.drop_duplicates(subset={'ZCTA5', 'ZPOP'}).drop(['STATE', 'COUNTY'], 1) 
zcta_ct_county = df['ZCTA5'].value_counts().reset_index() 
zcta_ct_county.columns = ['ZCTA5', 'CT_COUNTY'] 
pre_merge_1 = pd.merge(zcta_pop, zcta_ct_county, on='ZCTA5')[['ZCTA5', 'ZPOP', 'CT_COUNTY']] 

Answer 1

我想你需要添加reset_index，因为value_counts输出Series，需要DataFrame 2列：

zcta_ct_county = df['ZCTA5'].value_counts().reset_index()