熊猫:检查json对象中是否存在dataframe列

Question

我有一个名为“countries”的json对象，如下所示，所有国家都有ISO代码列表：

countries = [{"name":"Afghanistan","alpha-2":"AF","country-code":"004"},{"name":"Åland Islands","alpha-2":"AX","country-code":"248"},{"name":"Albania","alpha-2":"AL","country-code":"008"},{"name":"Algeria","alpha-2":"DZ","country-code":"012"}]

我有一个“国家”专栏的熊猫数据栏：

Country
--------
AU
AL
DZ

如何检查'Country‘列中的任何行是否存在于json对象的'alpha-2’列中，如果不存在则打印错误？

当我尝试下面的代码时，我不会发现任何错误，也不会打印任何内容。

if df['Country'].any() in [x['alpha-2'] for x in countries]:
    print "Country code exists"

Answer 1

你可以

if set(x['alpha-2'] for x in countries).intersection(df.Country):
    print('Country code exists')

或者，在精神上更接近你正在尝试的东西(但性能特征完全不同)，

if df.Country.isin(x['alpha-2'] for x in countries).any():
    print('Country code exists')

Answer 2

因为您已经有了一个熊猫DataFrame，所以可以将JSON对象转换为DataFrame，使用pd.merge对两者进行inner连接，然后检查返回的DataFrame是否为空。

>>> import pandas as pd
>>> countries_base = [{'Country': 'AU'}, {'Country': 'AL'}, {'Country': 'DZ'}]
>>> countries = [{"name":"Afghanistan","alpha-2":"AF","country-code":"004"},{"name":"Åland Islands","alpha-2":"AX","country-code":"248"},{"name":"Albania","alpha-2":"AL","country-code":"008"},{"name":"Algeria","alpha-2":"DZ","country-code":"012"}]
>>> df1 = pd.DataFrame(countries_base)
>>> df2 = pd.DataFrame(countries)
>>> m = pd.merge(df1, df2, how='inner', left_on='Country', right_on='alpha-2')
>>> if m.empty:
>>>     print('Country code does not exist') 
>>> else:
>>>     print('Country code exists')