如何使用while循环帮助索引/查找与string语句匹配的元素

Question

我试图创建一个函数，它接受一个参数，即一个国家，并为该国定位相邻的首都。例：

countries_and_capitals = (['Afghanistan', 'Kabul'], ['Albania', 'Tirana (Tirane)'], ['Algeria', 'Algiers'], ['Andorra', 'Andorra la Vella'],
['Angola', 'Luanda'], ['Antigua and Barbuda', "Saint John's"], ['Argentina', 'Buenos Aires'],
['Armenia', 'Yerevan'],
['Australia', 'Canberra']

def get_capital_from_the_country(cntry)

并在输入国家/地区后显示首都

Answer 1

一种方法是使用for循环并在解包两个值（country和capital）时迭代元组，然后如果找到与参数匹配的国家，则返回capital，如果没有找到国家，则返回消息（此方法更快）：

countries_and_capitals = (['Afghanistan', 'Kabul'], ['Albania', 'Tirana (Tirane)'], ['Algeria', 'Algiers'], ['Andorra', 'Andorra la Vella'],
['Angola', 'Luanda'], ['Antigua and Barbuda', "Saint John's"], ['Argentina', 'Buenos Aires'],
['Armenia', 'Yerevan'],
['Australia', 'Canberra'])


def get_capital_from_the_country(cntry):
    cntry = cntry.lower()
    for country, capital in countries_and_capitals:
        if country.lower() == cntry:
            return capital
    return 'Can\'t find that country'


print(get_capital_from_the_country('Afghanistan'))
# Kabul
print(get_capital_from_the_country('Afghanista'))
# Can't find that country
print(get_capital_from_the_country('afghanistan'))
# Kabul
print(get_capital_from_the_country('aFgHaniStan'))
# Kabul

另一种方法是将该元组转换为字典，然后通过使用.get（返回特定消息而不是引发KeyError）轻松访问键（国家）的值（大写）：

def get_capital_from_the_country(cntry):
    dct = {k.lower(): w for k, w in countries_and_capitals}
    # alternatively can use:
    # dct = dict(map(lambda x: (x[0].lower(), x[1]), countries_and_capitals))
    return dct.get(cntry.lower(), 'Can\'t find that country')