print的时候提示变量招不到？【求助】

import json

# load data into a list
filename = 'C:\Python\python_work\population_data.json'
with open(filename) as f:
    pop_data = json.load(f)

# print the Y2000 population for each country   

for pop_dict in pop_data:
    try:
        if pop_dict['Year'] == '2010':
            country_name = pop_dict['Country Name']
            population = pop_dict['Value']  
    except ValueError:
        print('missing data')
    else:   
        print(country_name + ": " + population)

系统提示NameError: name 'country_name' is not defined， 难道country_name只能在try block区间中有效么？

是没有考虑  pop_dict['Year'] ！= '2010' 的情况吧

import json

# load data into a list
filename = 'D:\TestProject\pycentosprj\population_data.json'
with open(filename) as f:
    #pop_data=[{"Year": "2010","Country Name": "CN","Value": "10"}]
    pop_data = json.load(f)
# print the Y2000 population for each country   

for pop_dict in pop_data:
    try:
        if pop_dict['Year'] == '2010':
            country_name = pop_dict['Country Name']
            population = pop_dict['Value']  
    except ValueError:
        print('missing data')
    else:   
        print(country_name + ": " + population)
以上是我在python3.6运行通过的代码，请参考。