我希望能够找到一个特定的数据块使用d

Question

这是一些数据的字典。当我打印它时，它会在两个不同的列中打印出来。我已经在这里寻找如何搜索它，并找到一个特定的数据块，但这是没有任何意义的我。如果你能告诉我如何通过这个搜索（使用日期），然后打印出数据，那将不胜感激

rainfall = {
    '01/08/2014':1.0,
    '21/01/2015':0.20,
    '22/01/2015':0.10,
    '23/01/2015':1.00,
    '24/01/2015':0.30,
    '25/01/2015':0.40,
    '26/01/2015':0.75,
    '27/01/2015':0.20,
    '28/01/2015':1.00,
    '29/01/2015':0.20,
    '30/01/2015':0.20,
    '31/01/2015':0.30,
    }

for k, v in rainfall.items():
    print(f'{k:<4} - {v}')


def searching_for_data():
    whatdata=input("What date would you like to find (format: DD/MM/YYYY)")
    if whatdata in rainfall:
        print(find(whatdata))


finddata=input("Would you like to find a specific piece of data?")
if finddata == "Yes":
    searching_for_data()

Answer 1

您需要更改：

if whatdata in rainfall:
    print(find(whatdata)

至

if whatdata in rainfall.keys():
    print(rainfall[whatdata])

Answer 2

可以重写函数以利用dict.__getitem__或其语法糖[]：

def searching_for_data():
    whatdata = input("What date would you like to find (format: DD/MM/YYYY)")
    if whatdata in rainfall:
        print(rainfall[whatdata])

但是你应该养成函数return值的习惯。当您希望看到None时，如果密钥不存在，上述解决方案也将不起任何作用。例如，使用dict.get：

def searching_for_data():
    """Return value if it exists in dictionary, else None"""
    whatdata = input("What date would you like to find (format: DD/MM/YYYY)")
    return rainfall.get(whatdata)

finddata = input("Would you like to find a specific piece of data?")
if finddata == "Yes":
    data = searching_for_data()
    print(data)

Answer 3

您可以在searching_for_data中使用get函数：

def searching_for_data():
    whatdata = input("What date would you like to find (format: DD/MM/YYYY)")
    print(rainfall.get(whatdata, 'No data for ' + whatdata))

如果该键不存在，它允许您定义一个默认值（或者为用户定义一条消息）

但是，更好的方法是让函数返回值并在顶层执行print命令：

def searching_for_data():
    whatdata = input("What date would you like to find (format: DD/MM/YYYY)")
    return rainfall.get(whatdata, 'No data for ' + whatdata)

...

print(searching_for_data())