Python 在MongoDB中只获取一次值

我的MongoDB中有一些文档。这些是产品。每xx小时/天对产品进行一次爬网。现在我一次又一次地得到同样的产品，但它们上的时间戳不同。很快价格也会改变

要创建每个产品的价格历史记录，我需要按ModelID查找（）产品。 ModelID对于每个产品都是唯一的。问题是：

如何获取“每个产品（ModelID）”1文档

你为什么需要这个？ 我想通过ModelID获得产品的名称，这样我就可以在网站上显示数据库中有哪些可用的产品

这是我收藏的一个例子：CPU:

db.CPU.find（）

键入“it”了解更多信息 它

键入“it”了解更多信息 它

键入“it”了解更多信息 它

因此，如果我只想要ModelID为BX80646I74790K的产品

find（{ModelID:'BX80646I74790K'}）

---

但是我只想要一次，我该怎么做呢？

你应该使用

distinct

。尝试使用：

db.CPU.distinct( 'ModelID' )

---

我的意思是我想得到所有的产品。但只有一次。我不要复制品

{ "_id" : ObjectId("54bc38fd02cebca524c4acda"), "Price" : 69.95, "Name" : "Intel Pentium G3450", "Type" : "CPU", "Brand" : "Intel", "ModelID" : "BX80646G3450", "Timestamp" : 1421621501 }
{ "_id" : ObjectId("54bc38ff02cebca524c4acdb"), "Price" : 849.95, "Name" : "Intel Core i7 4960X", "Type" : "CPU", "Brand" : "Intel", "ModelID" : "BX80633I74960X", "Timestamp" : 1421621503 }
{ "_id" : ObjectId("54bc390202cebca524c4acdc"), "Price" : 309.95, "Name" : "Intel Core i7 4820K", "Type" : "CPU", "Brand" : "Intel", "ModelID" : "BX80633I74820K", "Timestamp" : 1421621506 }
{ "_id" : ObjectId("54bc390402cebca524c4acdd"), "Price" : 295.95, "Name" : "Intel Core i7 4770", "Type" : "CPU", "Brand" : "Intel", "ModelID" : "BX80646I74770", "Timestamp" : 1421621508 }
{ "_id" : ObjectId("54bc390802cebca524c4acde"), "Price" : 154.95, "Name" : "Intel Core i3 4370", "Type" : "CPU", "Brand" : "Intel", "ModelID" : "BX80646I34370", "Timestamp" : 1421621512 }
{ "_id" : ObjectId("54bc390a02cebca524c4acdf"), "Price" : 139.95, "Name" : "Intel Core i3 4350", "Type" : "CPU", "Brand" : "Intel", "ModelID" : "BX80646I34350", "Timestamp" : 1421621514 }
{ "_id" : ObjectId("54bc390c02cebca524c4ace0"), "Price" : 129.95, "Name" : "Intel Core i3 4330", "Type" : "CPU", "Brand" : "Intel", "ModelID" : "BX80646I34330", "Timestamp" : 1421621516 }
{ "_id" : ObjectId("54bc390e02cebca524c4ace1"), "Price" : 122.95, "Name" : "Intel Core i3 4160", "Type" : "CPU", "Brand" : "Intel", "ModelID" : "BX80646I34160", "Timestamp" : 1421621518 }
{ "_id" : ObjectId("54bc391102cebca524c4ace2"), "Price" : 119.95, "Name" : "Intel Core i3 4150", "Type" : "CPU", "Brand" : "Intel", "ModelID" : "BX80646I34150", "Timestamp" : 1421621521 }
{ "_id" : ObjectId("54bc391302cebca524c4ace3"), "Price" : 119.95, "Name" : "Intel Core i3 4130", "Type" : "CPU", "Brand" : "Intel", "ModelID" : "BX80646I34130", "Timestamp" : 1421621523 }
{ "_id" : ObjectId("54bc391602cebca524c4ace4"), "Price" : 274.95, "Name" : "AMD FX-9590 Black Edition", "Type" : "CPU", "Brand" : "AMD", "ModelID" : "FD9590FHHKWOF", "Timestamp" : 1421621526 }
{ "_id" : ObjectId("54bc391702cebca524c4ace5"), "Price" : 199.95, "Name" : "AMD FX-9370 Black Edition", "Type" : "CPU", "Brand" : "AMD", "ModelID" : "FD9370FHHKWOF", "Timestamp" : 1421621527 }
{ "_id" : ObjectId("54bc391a02cebca524c4ace6"), "Price" : 88.95, "Name" : "AMD A8-6500", "Type" : "CPU", "Brand" : "AMD", "ModelID" : "AD6500OKHLBOX", "Timestamp" : 1421621530 }
{ "_id" : ObjectId("54bc391c02cebca524c4ace7"), "Price" : 84.95, "Name" : "AMD A6-7400K Black Edition", "Type" : "CPU", "Brand" : "AMD", "ModelID" : "AD740KYBJABOX", "Timestamp" : 1421621532 }
{ "_id" : ObjectId("54bc391e02cebca524c4ace8"), "Price" : 54.95, "Name" : "AMD A6-5400K", "Type" : "CPU", "Brand" : "AMD", "ModelID" : "AD540KOKHJBOX", "Timestamp" : 1421621534 }
{ "_id" : ObjectId("54bc392002cebca524c4ace9"), "Price" : 134.95, "Name" : "AMD A10-7700K Black Edition", "Type" : "CPU", "Brand" : "AMD", "ModelID" : "AD770KXBJABOX", "Timestamp" : 1421621536 }
{ "_id" : ObjectId("54bc392302cebca524c4acea"), "Price" : 229.95, "Name" : "Intel Core i5 3570K", "Type" : "CPU", "Brand" : "Intel", "ModelID" : "BX80637I53570K", "Timestamp" : 1421621539 }
{ "_id" : ObjectId("54bc63a702cebca816a786e3"), "Timestamp" : 1421632423, "Name" : "Intel Core i7 4790K", "Price" : 329.95, "Brand" : "Intel", "Type" : "CPU", "ModelID" : "BX80646I74790K" }
{ "_id" : ObjectId("54bc63aa02cebca816a786e4"), "Timestamp" : 1421632426, "Name" : "Intel Core i5 4670", "Price" : 194.95, "Brand" : "Intel", "Type" : "CPU", "ModelID" : "BX80646I54670" }
{ "_id" : ObjectId("54bc66ec02cebca8b84a7eef"), "Price" : 329.95, "Timestamp" : 1421633260, "ModelID" : "BX80646I74790K", "Brand" : "Intel", "Type" : "CPU", "Name" : "Intel Core i7 4790K" }

{ "_id" : ObjectId("54bc66f002cebca8b84a7ef0"), "Price" : 194.95, "Timestamp" : 1421633264, "ModelID" : "BX80646I54670", "Brand" : "Intel", "Type" : "CPU", "Name" : "Intel Core i5 4670" }
{ "_id" : ObjectId("54bc66f302cebca8b84a7ef1"), "Price" : 164.95, "Timestamp" : 1421633267, "ModelID" : "FD8350FRHKBOX", "Brand" : "AMD", "Type" : "CPU", "Name" : "AMD FX-8350 Black Edition" }
{ "_id" : ObjectId("54bc66f602cebca8b84a7ef2"), "Price" : 209.95, "Timestamp" : 1421633270, "ModelID" : "BX80646I54690", "Brand" : "Intel", "Type" : "CPU", "Name" : "Intel Core i5 4690" }
{ "_id" : ObjectId("54bc66f802cebca8b84a7ef3"), "Price" : 188.95, "Timestamp" : 1421633272, "ModelID" : "BX80646I54590", "Brand" : "Intel", "Type" : "CPU", "Name" : "Intel Core i5 4590" }
{ "_id" : ObjectId("54bc66fa02cebca8b84a7ef4"), "Price" : 319.95, "Timestamp" : 1421633274, "ModelID" : "BX80637I73770K", "Brand" : "Intel", "Type" : "CPU", "Name" : "Intel Core i7 3770K" }
{ "_id" : ObjectId("54bc66fc02cebca8b84a7ef5"), "Price" : 84.95, "Timestamp" : 1421633276, "ModelID" : "FD4300WMHKBOX", "Brand" : "AMD", "Type" : "CPU", "Name" : "AMD FX-4300" }
{ "_id" : ObjectId("54bc66fe02cebca8b84a7ef6"), "Price" : 99.95, "Timestamp" : 1421633278, "ModelID" : "FD6300WMHKBOX", "Brand" : "AMD", "Type" : "CPU", "Name" : "AMD FX-6300 Black Edition" }
{ "_id" : ObjectId("54bc670002cebca8b84a7ef7"), "Price" : 549.95, "Timestamp" : 1421633280, "ModelID" : "BX80648I75930K", "Brand" : "Intel", "Type" : "CPU", "Name" : "Intel Core I7 5930K" }
{ "_id" : ObjectId("54bc670202cebca8b84a7ef8"), "Price" : 189.95, "Timestamp" : 1421633282, "ModelID" : "BX80646I54460", "Brand" : "Intel", "Type" : "CPU", "Name" : "Intel Core i5 4460" }
{ "_id" : ObjectId("54bc674c02cebca8d0ccf375"), "ModelID" : "BX80646I74790K", "Timestamp" : 1421633356, "Type" : "CPU", "Brand" : "Intel", "Price" : 329.95, "Name" : "Intel Core i7 4790K" }
{ "_id" : ObjectId("54bc674d02cebca8d0ccf376"), "ModelID" : "BX80646I54670", "Timestamp" : 1421633357, "Type" : "CPU", "Brand" : "Intel", "Price" : 194.95, "Name" : "Intel Core i5 4670" }
{ "_id" : ObjectId("54bc674f02cebca8d0ccf377"), "ModelID" : "FD8350FRHKBOX", "Timestamp" : 1421633359, "Type" : "CPU", "Brand" : "AMD", "Price" : 164.95, "Name" : "AMD FX-8350 Black Edition" }
{ "_id" : ObjectId("54bc675202cebca8d0ccf378"), "ModelID" : "BX80646I54690", "Timestamp" : 1421633362, "Type" : "CPU", "Brand" : "Intel", "Price" : 209.95, "Name" : "Intel Core i5 4690" }
{ "_id" : ObjectId("54bc689f02cebca9626f7e27"), "ModelID" : "BX80646I74790K", "Timestamp" : 1421633695, "Brand" : "Intel", "Type" : "CPU", "Name" : "Intel Core i7 4790K", "Price" : 329.95 }
{ "_id" : ObjectId("54bc68a102cebca9626f7e28"), "ModelID" : "BX80646I54670", "Timestamp" : 1421633697, "Brand" : "Intel", "Type" : "CPU", "Name" : "Intel Core i5 4670", "Price" : 194.95 }
{ "_id" : ObjectId("54bc68a402cebca9626f7e29"), "ModelID" : "FD8350FRHKBOX", "Timestamp" : 1421633700, "Brand" : "AMD", "Type" : "CPU", "Name" : "AMD FX-8350 Black Edition", "Price" : 164.95 }
{ "_id" : ObjectId("54bc68a602cebca9626f7e2a"), "ModelID" : "BX80646I54690", "Timestamp" : 1421633702, "Brand" : "Intel", "Type" : "CPU", "Name" : "Intel Core i5 4690", "Price" : 209.95 }
{ "_id" : ObjectId("54bc68a802cebca9626f7e2b"), "ModelID" : "BX80646I54590", "Timestamp" : 1421633704, "Brand" : "Intel", "Type" : "CPU", "Name" : "Intel Core i5 4590", "Price" : 188.95 }
{ "_id" : ObjectId("54bc696002cebca99c34f39c"), "Brand" : "Intel", "Name" : "Intel Core i7 4790K", "Price" : 329.95, "Timestamp" : 1421633888, "ModelID" : "BX80646I74790K", "Type" : "CPU" }
{ "_id" : ObjectId("54bc696202cebca99c34f39d"), "Brand" : "Intel", "Name" : "Intel Core i5 4670", "Price" : 194.95, "Timestamp" : 1421633890, "ModelID" : "BX80646I54670", "Type" : "CPU" }

{ "_id" : ObjectId("54bc696402cebca99c34f39e"), "Brand" : "AMD", "Name" : "AMD FX-8350 Black Edition", "Price" : 164.95, "Timestamp" : 1421633892, "ModelID" : "FD8350FRHKBOX", "Type" : "CPU" }
{ "_id" : ObjectId("54bc696602cebca99c34f39f"), "Brand" : "Intel", "Name" : "Intel Core i5 4690", "Price" : 209.95, "Timestamp" : 1421633894, "ModelID" : "BX80646I54690", "Type" : "CPU" }
{ "_id" : ObjectId("54bc696802cebca99c34f3a0"), "Brand" : "Intel", "Name" : "Intel Core i5 4590", "Price" : 188.95, "Timestamp" : 1421633896, "ModelID" : "BX80646I54590", "Type" : "CPU" }

{ "_id" : ObjectId("54bc38cd02cebca524c4acc6"), "Price" : 329.95, "Name" : "Intel Core i7 4790K", "Type" : "CPU", "Brand" : "Intel", "ModelID" : "BX80646I74790K", "Timestamp" : 1421621453 }
{ "_id" : ObjectId("54bc63a702cebca816a786e3"), "Timestamp" : 1421632423, "Name" : "Intel Core i7 4790K", "Price" : 329.95, "Brand" : "Intel", "Type" : "CPU", "ModelID" : "BX80646I74790K" }
{ "_id" : ObjectId("54bc66ec02cebca8b84a7eef"), "Price" : 329.95, "Timestamp" : 1421633260, "ModelID" : "BX80646I74790K", "Brand" : "Intel", "Type" : "CPU", "Name" : "Intel Core i7 4790K" }
{ "_id" : ObjectId("54bc674c02cebca8d0ccf375"), "ModelID" : "BX80646I74790K", "Timestamp" : 1421633356, "Type" : "CPU", "Brand" : "Intel", "Price" : 329.95, "Name" : "Intel Core i7 4790K" }
{ "_id" : ObjectId("54bc689f02cebca9626f7e27"), "ModelID" : "BX80646I74790K", "Timestamp" : 1421633695, "Brand" : "Intel", "Type" : "CPU", "Name" : "Intel Core i7 4790K", "Price" : 329.95 }
{ "_id" : ObjectId("54bc696002cebca99c34f39c"), "Brand" : "Intel", "Name" : "Intel Core i7 4790K", "Price" : 329.95, "Timestamp" : 1421633888, "ModelID" : "BX80646I74790K", "Type" : "CPU" }

db.CPU.distinct( 'ModelID' )