python - 用相应的工作日数字替换列表中的工作日字符串 ("MON"、 "TUE"等)

Question

我让用户选择工作日的字符串，然后将其存储在列表中。我的目标是用它对应的 weekday number 替换任何用户选择的字符串.我的代码有效，但它似乎不必要地庞大。有没有更优雅的方式？

selected_weekdays = ["MON", "WED", "THU", "SAT"]

for i in range(len (selected_weekdays)):
    if selected_weekdays[i] == "MON":
        selected_weekdays[i] = 0
    elif selected_weekdays[i] == "TUE":
        selected_weekdays[i] = 1
    elif selected_weekdays[i] == "WED":
        selected_weekdays[i] = 2
    elif selected_weekdays[i] == "THU":
        selected_weekdays[i] = 3
    elif selected_weekdays[i] == "FRI":
        selected_weekdays[i] = 4
    elif selected_weekdays[i] == "SAT":
        selected_weekdays[i] = 5
    elif selected_weekdays[i] == "SUN":
        selected_weekdays[i] = 6
    else:
        pass

print(selected_weekdays)

正确的输出:

[0, 2, 3, 5]

Answer 1

您可以通过生成字典映射来避免一些额外的工作

最好避免修改您也出于各种原因迭代的结构
参见 Modifying list while iterating

字典 .get() 方法将选择一个默认选项(在您的原始情况下是工作日，尽管您可能想更改它以使其成为其中之一

• 未列出的工作日(这是您的代码当前所做的，所以我保持结果不变)
• 异常(KeyError 来自直接索引 [] .. 你可能希望它突出显示错误)
• None(基本上丢弃错误的值，并且很容易在下一步中过滤)

# dictionary expression
weekday_mapping = {day: index for index, day in enumerate((
    "MON", "TUE", "WED", "THU", "FRI", "SAT", "SUN"))}

selected_weekdays = ["MON", "WED", "THU", "SAT"]
results = []
for weekday in selected_weekdays:
    results.append(weekday_mapping.get(weekday, weekday))

>>> results
[0, 2, 3, 5]
>>> selected_weekdays = ["MON", "WED", "THU", "FakeDay", "SAT"]
...
>>> results
[0, 2, 3, 'FakeDay', 5]