Question

我有一个列表：

[Table(Name = "ClassA")]
public class ClassA
{
    public ClassA()
    {
        LinksToClassB = new EntitySet<ClassB>();
    }

    [Column(IsPrimaryKey = true, IsDbGenerated = true, AutoSync = AutoSync.OnInsert, DbType = "Int NOT NULL IDENTITY")]
    public int ID { get; set; }

    [Association]
    public EntitySet<ClassB> LinksToClassB { get; set; } //=> 1 to n cardinality

    [Association]
    public ClassB OneLinkToClassB { get; set; }//=> 1 to 1 cardinality
}


[Table(Name = "ClassB")]
public class ClassB
{
    [Column(IsPrimaryKey = true, IsDbGenerated = true, AutoSync = AutoSync.OnInsert, DbType = "Int NOT NULL IDENTITY")]
    public int ID { get; set; }

    [Column(CanBeNull = true)]
    public string Name { get; set; }
}

public class DatabaseContext : DataContext
{
    public Table<ClassA> ClassATable;
    public Table<ClassB> ClassBTable;

    public DatabaseContext(string connection) : base(connection) { }
}



[TestClass]
public class Test
{
    string path = @"F:\Temp\Testspace - Forum Database\database.mdf";//path to database

    [TestMethod]
    public void TestMethod()
    {
        //creates Database
        DatabaseContext context = new DatabaseContext(path);

        if (context.DatabaseExists())//Delete if exists
        {
            context.DeleteDatabase();
        }

        context.CreateDatabase();

        ClassB b1 = new ClassB(); b1.Name = "name 1";
        ClassB b2 = new ClassB(); b2.Name = "name 2";
        ClassB b3 = new ClassB(); b3.Name = "name 3";

        ClassA a = new ClassA();

        //now the references will be added to the object a

        //in 1-n references
        a.LinksToClassB.Add(b1);
        a.LinksToClassB.Add(b2);
        a.LinksToClassB.Add(b3);

        //and the has-one reference (OneLinkToClassB)
        a.OneLinkToClassB = b1;


        context.ClassATable.InsertOnSubmit(a);

        context.SubmitChanges(); //store in database


        //now the database will be reloaded
        context = new DatabaseContext(path);


        //Check if all ClassB objects were correctly stored and reloaded
        foreach (ClassB x in context.ClassBTable)
        {
            Console.WriteLine(x.ID + "; " + x.Name);
            /*    
                -> expected output:
                    1; name 1
                    2; name 2
                    3; name 3
                -> real output
                    1; name 1
                    2; name 2
                    3; name 3

                -> check!
            */
        }

        //check if all ClassA objects were correctly stored and reloaded
        foreach (ClassA x in context.ClassATable)//context.ClassATable has only one entry
        {
            Console.WriteLine("check of entitys set");

            //check of 1-n references
            foreach (ClassB b in x.LinksToClassB)
            {
                Console.WriteLine(x.ID + " has a link to " + b.ID + ", " + b.Name);
                /*
                    -> expected output:
                        1 has a link to 1, name 1
                        1 has a link to 2, name 2
                        1 has a link to 3, name 3

                    -> real output
                        1 has a link to 1, name 1

                    -> doesn't match...
                */
            }


            Console.WriteLine("check of single link");

            //check of 1-1 reference
            Console.WriteLine(x.ID + " has a link to " + x.OneLinkToClassB.ID + ", " + x.OneLinkToClassB.Name);
            /*
                    -> expected output:
                        1 has a link to 1, name 1

                    -> real output
                        this line throws an NullReferenceException
            */
        }
    }
}

我想做点什么

mylist = [{2: 1451989654}, {3: 1435222955}, {4: 1346726067}, {53: 1451887667}, {723: 1445763454}]

我最好能做到这一点吗？

Answer 1

mylist是一个列表，因此您需要首先遍历列表：

for dct in mylist:
    for key, val in dct.items():
        print key
        print val

注意：您需要dict.items()（或.iteritems()）来获取密钥和值

Answer 2

由于您的词典中没有重复的键，为什么要将它保存在列表中？

您可以将所有内容保存在一个词典中（或稍后再转换），这样就可以更轻松地访问数据（包括打印）：

mylist = [{2: 1451989654}, {3: 1435222955}, {4: 1346726067}, {53: 1451887667}, {723: 1445763454}]
mydict = {k:d[k] for d in mylist for k in d} # Convert the list to one dictionary
for k in mydict:
    print k, mydict[k]

并打印出来：

2 1451989654
3 1435222955
4 1346726067
53 1451887667
723 1445763454

但请注意，如果您想要订购数据，则可能需要默认为OrderedDict并将转换替换为：

mydict = OrderedDict([(k, d[k]) for d in mylist for k in d])

如何循环遍历词典列表？

2 个答案: