[英]How do I print a list choosen by the user via input?
我在python程序中定義了兩個列表,我通過input("...")
函數獲取用戶輸入。
應該向用戶輸入列表名稱,以便我可以將其打印到控制台,問題是我只能打印列表名稱,而不能打印實際列表本身。
這是我的清單:
aaa = [1,2,3,4,5]
bbb = [6,7,8,9,10]
這是我使用的獲取用戶輸入的代碼:
a = input("Input list name")
這是我用來打印列表的代碼:
print(a)
這是預期的輸出:
[1, 2, 3, 4, 5]
相反,這是我得到的輸出:
aaa
您輸入的內容是str
並且在執行print(a)
時嘗試打印字符串而不是列表。
您需要了解str
和變量名不是同一回事。
aaa
與'aaa'
您可以在這種情況下使用dict
# store your lists in dict as below
d = {'aaa': [1,2,3,4,5], 'bbb':[6,7,8,9,10]}
a=input('Input list name: ')
# this will handle if user input does not match to any key in dict
try:
print(d[a])
except:
print("Please enter correct name for list")
輸出:
[1,2,3,4,5]
嘗試使用locals()
函數,如下所示:
aaa = [1, 2, 3, 4, 5]
bbb = [6, 7, 8, 9, 10]
target = input("What list would you like to see? ")
# NOTE: please don't (I REPEAT DON'T) use eval here
# : it WILL cause security flaws
# : try to avoid eval as much as possible
if target in locals():
found = locals()[target]
# basic type checking if you only want the user to be able to print lists
if type(found) == list:
print(found)
else:
print("Whoops! You've selected a value that isn't a list!")
else:
print("Oh no! The list doesn't exist")
這是相同代碼的更簡潔版本:
aaa = [1, 2, 3, 4, 5]
bbb = [6, 7, 8, 9, 10]
target = input("Enter list name: ")
if target in locals():
found = locals()[target]
print(found if type(found) == list else "Value is not a list.")
else:
print("Target list doesn't exist")
注意:第二個答案中的代碼較小,因為我刪除了注釋,使用了較小的消息並添加了三元運算符。
注:查看這個答案從這個問題 ,以了解更多關於為什么使用eval
是壞的。
祝好運。
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