Question

我想要做的是制作一个祖先的字典，我已经成功了。我唯一的问题是，当一段关系不存在时，我的程序应该输出＆＃34;关系不在字典中。＆＃34;当密钥不在字典中时，我知道如何做到这一点，但是如何使用值？

这是我的代码：

relationships = {"Jalen": "Joseph", "Arthur": "Joseph", "Mike": "Joseph", "Chris": "Joseph", "Joseph": "Thomas", "Jesse": "Marcus", "Marcus": "Gerhard", "Gerhard": "Allan", "Allan": "Thomas", "James": "Gerhard"}
print relationships

def menu():
    print ("To find a father, press 1.")
    print ("To find a grandfather, press 2.")
    print ("To find a great-grandfather, press 3.")
    print ("To exit the program, press 0,")
    while True:
        choice = input("Enter your choice of action: ")
        if (choice >= 0) and (choice <= 3):
            return choice
        else:
            print("Invalid option. Enter an integer from 0 to 3")

def father(n):
    if relationships.has_key(n):
        return relationships[n]

def grandfather(n):
    if relationships.has_key(n):
        father = relationships[n]
        if relationships.has_key(father):
            return relationships[father]

def greatgrandfather(n):
    if relationships.has_key(n):
        father = relationships[n]
        if relationships.has_key(father):
            grandfather = relationships[father]
            if relationships.has_key(grandfather):
                return relationships[grandfather]

def main ():
    while True:
        choice = menu()
        if choice == 0:
            break
        else:
            name = raw_input("Please enter the name of the person for whom you seek an ancestory: ")
            if relationships[name]:
                if choice == 1:
                    print "The father of ", name, " is ", father(name), "."
                elif choice == 2:
                    print "The grandfather of ", name, " is ", grandfather(name), "."
                else:
                    print "The great-grandfather of ", name, " is ", greatgrandfather(name), "."
            else:
                print "This relationship is not in our records."


main()

我如何检查值中是否存在关系？ Python语言。

Answer 1

in关键字用于检查值或键是否在字典中。因此，您需要做的就是检查字典中是否存在密钥：

if record not in relationships:
    print "This relationship is not in our records.

Answer 2

我不知道正在引发哪个错误，但我认为这是一个KeyError，在这一行中

if relationships[name]:

如果不存在关系[name]，则会引发异常。更好的代码是使用

if relationships.get(name, ''):

这样，如果name不在字典中，它就不会读取if statement内的代码。

如评论中所述，另一种方法是

if name in relationships:

Answer 3

if aRelationship in relationships.values():
    #aRelationship in relationships.values()
else:
    #aRelationship  not in relationships.values()

我正在从字典中建立关系，但有人可以帮我修复一个我无法弄清楚的输出吗？

3 个答案: