打印字典時出現KeyError？

Question

因此，我正在嘗試編寫一個程序，讓用戶輸入課程編號，然后獲取該課程的房間、講師和會議時間信息。 如果用戶輸入未找到/無效的課程，我希望能夠打印終止消息，但是當我嘗試時，它會出現 KeyError。 我曾嘗試使用 try/except 語句，但是當我執行代碼時出現了 TypeError。

room_dict = {
    "CS101": {
        "Room": "3004"
    },
    "CS102": {
        "Room": "4501"
    },
    "CS103": {
        "Room": "6755"
    },
    "NT110": {
        "Room": "1244"
    },
    "CM241": {
        "Room": "1411"
    },
}


instructor_dict = {
    "CS101": {
        "Instructor": "Haynes"
    },
    "CS102": {
        "Instructor": "Alvarado"
    },
    "CS103": {
        "Instructor": "Rich"
    },
    "NT110": {
        "Instructor": "Burkes"
    },
    "CM241": {
        "Instructor": "Lee"
    },
}


time_dict = {
    "CS101": {
        "Time": "8:00 a.m."
    },
    "CS102": {
        "Time": "9:00 a.m."
    },
    "CS103": {
        "Time": "10:00 a.m."
    },
    "NT110": {
        "Time": "11:00 a.m."
    },
    "CM241": {
        "Time": "1:00 p.m."
    },
}

courses = {"CS101", "CS102", "CS103", "NT110", "CM241"}
dicts = {'Room':room_dict,'Instructor':instructor_dict,'Time': time_dict}

dash_count = 50
dashes = dash_count * "-"

print(f'College Course Locater Program')
print(f'Enter a course number below to get information')
get_course = input(f'Enter a course number: ')
print(dashes)

course_num = get_course
room = room_dict[get_course]
instructor = instructor_dict[get_course]
time = time_dict[get_course]

if course_num in courses:
    print(f'The details for course {get_course} are: ')
    print(f"Room: {room['Room']}")
    print(f"Time: {time['Time']}")
    print(f"Instructor: {instructor['Instructor']}")

else: print(course_num, '是無效的課程編號。')

基本上，我得到的 output 是：

College Course Locater Program
Enter a course number below to get information
Enter a course number: CS # where CS is an invalid course number
--------------------------------------------------
Traceback (most recent call last):
  File "C:\Users\Python\Downloads\courseinfo.py", line 75, in <module>
    room = room_dict[get_course]
KeyError: 'CS'

我正在尋找的是：

College Course Locater Program
Enter a course number below to get information
Enter a course number: CS
--------------------------------------------------
(course number) is an invalid course number. # where (course number) is an invalid course number

Answer 1

多個問題：

首先，您檢查if get_course == room_dict: 。 但是room_dict是整個字典！ 它永遠不能等於您輸入的課程編號。

其次，不需要循環for item in room_dict.items(): 。 字典中的值應該使用它們的鍵來訪問。 所以你會做類似的事情

get_course = input(f'Enter a course number: ')

print(f'The details for course {get_course} are: ')
room = room_dict[get_course]
instructor = instructor_dict[get_course]
time = time_dict[get_course]
print(f"Room: {room['Room']}, Time: {time['Time']}, Instructor: {instructor['Instructor']}")

當然，您需要確保get_course作為鍵存在於所有這些詞典中。 你可以這樣做

• 通過檢查密鑰是否明確存在，在跳躍之前查看： if get_course in room_dict:或者，
• 使用 try-except 捕獲 KeyError。 畢竟，請求原諒比允許更容易

try:
    room = room_dict[get_course]
    instructor = instructor_dict[get_course]
    time = time_dict[get_course]
except KeyError:
    print("Course info not found")

更好的是，您可以重新定義您的字典，以便一個字典包含有關課程的所有信息。

course_info = {
    "CS101": {
        "Room": "3004",
        "Instructor": "Haynes",
        "Time": "8:00 a.m."
    },
    "CS102": {
        "Room": "4501",
       "Instructor": "Alvarado",
       "Time": "9:00 a.m."
    }
# and so on
}

然后簡單地做：

get_course = input(f'Enter a course number: ')

try:
    crs = course_info[get_course]
    print(f'The details for course {get_course} are: ')
    print(f"Room: {crs['Room']}, Time: {crs['Time']}, Instructor: {crs['Instructor']}")
except KeyError:
    print(f"Details not found for {get_course}")

Answer 2

下面的代碼應該會讓你的生活更輕松。

它使用course_name = 'CM241'僅用於演示目的。

room_dict = {
    "CS101": {
        "Room": "3004"
    },
    "CS102": {
        "Room": "4501"
    },
    "CS103": {
        "Room": "6755"
    },
    "NT110": {
        "Room": "1244"
    },
    "CM241": {
        "Room": "1411"
    },
}


instructor_dict = {
    "CS101": {
        "Instructor": "Haynes"
    },
    "CS102": {
        "Instructor": "Alvarado"
    },
    "CS103": {
        "Instructor": "Rich"
    },
    "NT110": {
        "Instructor": "Burkes"
    },
    "CM241": {
        "Instructor": "Lee"
    },
}


time_dict = {
    "CS101": {
        "Time": "8:00 a.m."
    },
    "CS102": {
        "Time": "9:00 a.m."
    },
    "CS103": {
        "Time": "10:00 a.m."
    },
    "NT110": {
        "Time": "11:00 a.m."
    },
    "CM241": {
        "Time": "1:00 p.m."
    },
}

dicts = {'Time':time_dict,'Room':room_dict,'Instructor': instructor_dict}
course_name = 'CM241'
for k,v in dicts.items():
  print(f'{k} --> {v[course_name][k]}')

output

Time --> 1:00 p.m.
Room --> 1411
Instructor --> Lee