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给出列表生成Python字典的最有效方法

[英]Most efficient way to produce a Python dictionary given a list

 原文  2013-01-17 17:14:15  5   1    python/ performance/ optimization/ data-structures

问题描述

我正在寻找以下问题的优化（我有一些工作代码，但我很确定它可能会更快，写得很糟糕）。 我有一个SKU列表（6到9位数字），我正在亚马逊上查找信息。 工作代码如下： 

def buildDictionary2(stringy):
    x = stringy.xpath('//sellersku/text()|//product/descendant::amount[1]/text()')
    Sku_To_Price = {}
    for items in range(len(x)):
        if x[items] in myList:
            try:
                if x[items+1] not in myList:
                    Sku_To_Price[x[items]] = x[items+1]
                else:
                    Sku_To_Price[x[items]] = ''
            except:
                pass
        else:
            pass
    return Sku_To_Price

其中x是一般交替的SKU和价格的字典。 但是，由于无法找到价格，因此出现了复杂情况。 在这种情况下，列表（x）是SKU，SKU而不是SKU价格。

目前我正在查找SKU列表（在全局变量myList中），但无法帮助实现时间复杂度O（e ^ n）。 鉴于我正在寻找20,000个SKU区域的工作，我宁愿不是这样。

有没有办法使这个不那么复杂 - 所需的输出是一个字典，每个SKU一次（作为一个键），它的相应价格作为价值（如果没有价格，没有条目）。

编辑：

正在解析的XML示例 

<?xml version="1.0" ?>
<GetLowestOfferListingsForSKUResponse xmlns="http://mws.amazonservices.com/schema/Products/2011-10-01">
  <GetLowestOfferListingsForSKUResult SellerSKU="X" status="Success">
    <AllOfferListingsConsidered>true</AllOfferListingsConsidered>
    <Product xmlns="http://mws.amazonservices.com/schema/Products/2011-10-01" 
             xmlns:ns2="http://mws.amazonservices.com/schema/Products/2011-10-01/default.xsd">
      <Identifiers>
        <MarketplaceASIN>
          <MarketplaceId>X</MarketplaceId>
          <ASIN>X</ASIN>
        </MarketplaceASIN>
        <SKUIdentifier>
          <MarketplaceId>X</MarketplaceId>
          <SellerId>X</SellerId>
          <SellerSKU>10065897</SellerSKU>
        </SKUIdentifier>
      </Identifiers>
      <LowestOfferListings>
        <LowestOfferListing>
          <Qualifiers>
            <ItemCondition>New</ItemCondition>
            <ItemSubcondition>New</ItemSubcondition>
            <FulfillmentChannel>Amazon</FulfillmentChannel>
            <ShipsDomestically>True</ShipsDomestically>
            <ShippingTime>
              <Max>X</Max>
            </ShippingTime>
            <SellerPositiveFeedbackRating>X</SellerPositiveFeedbackRating>
          </Qualifiers>
          <NumberOfOfferListingsConsidered>3</NumberOfOfferListingsConsidered>
          <SellerFeedbackCount>X</SellerFeedbackCount>
          <Price>
            <LandedPrice>
              <CurrencyCode>X</CurrencyCode>
              <Amount>23.68</Amount>
            </LandedPrice>
            <ListingPrice>
              <CurrencyCode>X</CurrencyCode>
              <Amount>X</Amount>
            </ListingPrice>
            <Shipping>
              <CurrencyCode>X</CurrencyCode>
              <Amount>X</Amount>
            </Shipping>
          </Price>
          <MultipleOffersAtLowestPrice>False</MultipleOffersAtLowestPrice>
        </LowestOfferListing>
        <LowestOfferListing>
          <Qualifiers>
            <ItemCondition>X</ItemCondition>
            <ItemSubcondition>X</ItemSubcondition>
            <FulfillmentChannel>Merchant</FulfillmentChannel>
            <ShipsDomestically>X</ShipsDomestically>
            <ShippingTime>
              <Max>X</Max>
            </ShippingTime>
            <SellerPositiveFeedbackRating>X</SellerPositiveFeedbackRating>
          </Qualifiers>
          <NumberOfOfferListingsConsidered>X</NumberOfOfferListingsConsidered>
          <SellerFeedbackCount>X</SellerFeedbackCount>
          <Price>
            <LandedPrice>
              <CurrencyCode>X</CurrencyCode>
              <Amount>X</Amount>
            </LandedPrice>
            <ListingPrice>
              <CurrencyCode>X</CurrencyCode>
              <Amount>X</Amount>
            </ListingPrice>
            <Shipping>
              <CurrencyCode>X</CurrencyCode>
              <Amount>X</Amount>
            </Shipping>
          </Price>
          <MultipleOffersAtLowestPrice>X</MultipleOffersAtLowestPrice>
        </LowestOfferListing>
        <LowestOfferListing>
          <Qualifiers>
            <ItemCondition>X</ItemCondition>
            <ItemSubcondition>X</ItemSubcondition>
            <FulfillmentChannel>X</FulfillmentChannel>
            <ShipsDomestically>X</ShipsDomestically>
            <ShippingTime>
              <Max>X</Max>
            </ShippingTime>
            <SellerPositiveFeedbackRating>X</SellerPositiveFeedbackRating>
          </Qualifiers>
          <NumberOfOfferListingsConsidered>X</NumberOfOfferListingsConsidered>
          <SellerFeedbackCount>X</SellerFeedbackCount>
          <Price>
            <LandedPrice>
              <CurrencyCode>X</CurrencyCode>
              <Amount>X</Amount>
            </LandedPrice>
            <ListingPrice>
              <CurrencyCode>X</CurrencyCode>
              <Amount>X</Amount>
            </ListingPrice>
            <Shipping>
              <CurrencyCode>X</CurrencyCode>
              <Amount>X</Amount>
            </Shipping>
          </Price>
          <MultipleOffersAtLowestPrice>X</MultipleOffersAtLowestPrice>
        </LowestOfferListing>
        <LowestOfferListing>
          <Qualifiers>
            <ItemCondition>X</ItemCondition>
            <ItemSubcondition>X</ItemSubcondition>
            <FulfillmentChannel>X</FulfillmentChannel>
            <ShipsDomestically>X</ShipsDomestically>
            <ShippingTime>
              <Max>X</Max>
            </ShippingTime>
            <SellerPositiveFeedbackRating>X</SellerPositiveFeedbackRating>
          </Qualifiers>
          <NumberOfOfferListingsConsidered>X</NumberOfOfferListingsConsidered>
          <SellerFeedbackCount>X</SellerFeedbackCount>
          <Price>
            <LandedPrice>
              <CurrencyCode>X</CurrencyCode>
              <Amount>X</Amount>
            </LandedPrice>
            <ListingPrice>
              <CurrencyCode>X</CurrencyCode>
              <Amount>X</Amount>
            </ListingPrice>
            <Shipping>
              <CurrencyCode>X</CurrencyCode>
              <Amount>X</Amount>
            </Shipping>
          </Price>
          <MultipleOffersAtLowestPrice>X</MultipleOffersAtLowestPrice>
        </LowestOfferListing>
        <LowestOfferListing>
          <Qualifiers>
            <ItemCondition>X</ItemCondition>
            <ItemSubcondition>X</ItemSubcondition>
            <FulfillmentChannel>X</FulfillmentChannel>
            <ShipsDomestically>X</ShipsDomestically>
            <ShippingTime>
              <Max>X</Max>
            </ShippingTime>
            <SellerPositiveFeedbackRating>X</SellerPositiveFeedbackRating>
          </Qualifiers>
          <NumberOfOfferListingsConsidered>X</NumberOfOfferListingsConsidered>
          <SellerFeedbackCount>X</SellerFeedbackCount>
          <Price>
            <LandedPrice>
              <CurrencyCode>X</CurrencyCode>
              <Amount>X</Amount>
            </LandedPrice>
            <ListingPrice>
              <CurrencyCode>X</CurrencyCode>
              <Amount>X</Amount>
            </ListingPrice>
            <Shipping>
              <CurrencyCode>X</CurrencyCode>
              <Amount>X</Amount>
            </Shipping>
          </Price>
          <MultipleOffersAtLowestPrice>X</MultipleOffersAtLowestPrice>
        </LowestOfferListing>
      </LowestOfferListings>
    </Product>
  </GetLowestOfferListingsForSKUResult>
  <GetLowestOfferListingsForSKUResult SellerSKU="X" status="X">
    <AllOfferListingsConsidered>X</AllOfferListingsConsidered>
    <Product xmlns="http://mws.amazonservices.com/schema/Products/2011-10-01"
             xmlns:ns2="http://mws.amazonservices.com/schema/Products/2011-10-01/default.xsd">
      <Identifiers>
        <MarketplaceASIN>
          <MarketplaceId>X</MarketplaceId>
          <ASIN>X</ASIN>
        </MarketplaceASIN>
        <SKUIdentifier>
          <MarketplaceId>X</MarketplaceId>
          <SellerId>X</SellerId>
          <SellerSKU>9854521</SellerSKU>
        </SKUIdentifier>
      </Identifiers>
      <LowestOfferListings>
        <LowestOfferListing>
          <Qualifiers>
            <ItemCondition>X</ItemCondition>
            <ItemSubcondition>X</ItemSubcondition>
            <FulfillmentChannel>X</FulfillmentChannel>
            <ShipsDomestically>X</ShipsDomestically>
            <ShippingTime>
              <Max>X</Max>
            </ShippingTime>
            <SellerPositiveFeedbackRating>X</SellerPositiveFeedbackRating>
          </Qualifiers>
          <NumberOfOfferListingsConsidered>1</NumberOfOfferListingsConsidered>
          <SellerFeedbackCount>X</SellerFeedbackCount>
          <Price>
            <LandedPrice>
              <CurrencyCode>X</CurrencyCode>
              <Amount>2.68</Amount>
            </LandedPrice>
            <ListingPrice>
              <CurrencyCode>X</CurrencyCode>
              <Amount>X</Amount>
            </ListingPrice>
            <Shipping>
              <CurrencyCode>X</CurrencyCode>
              <Amount>X</Amount>
            </Shipping>
          </Price>
          <MultipleOffersAtLowestPrice>X</MultipleOffersAtLowestPrice>
        </LowestOfferListing>
        <LowestOfferListing>
          <Qualifiers>
            <ItemCondition>X</ItemCondition>
            <ItemSubcondition>X</ItemSubcondition>
            <FulfillmentChannel>X</FulfillmentChannel>
            <ShipsDomestically>X</ShipsDomestically>
            <ShippingTime>
              <Max>X</Max>
            </ShippingTime>
            <SellerPositiveFeedbackRating>X</SellerPositiveFeedbackRating>
          </Qualifiers>
          <NumberOfOfferListingsConsidered>8</NumberOfOfferListingsConsidered>
          <SellerFeedbackCount>X</SellerFeedbackCount>
          <Price>
            <LandedPrice>
              <CurrencyCode>X</CurrencyCode>
              <Amount>X</Amount>
            </LandedPrice>
            <ListingPrice>
              <CurrencyCode>X</CurrencyCode>
              <Amount>X</Amount>
            </ListingPrice>
            <Shipping>
              <CurrencyCode>X</CurrencyCode>
              <Amount>X</Amount>
            </Shipping>
          </Price>
          <MultipleOffersAtLowestPrice>X</MultipleOffersAtLowestPrice>
        </LowestOfferListing>
        <LowestOfferListing>
          <Qualifiers>
            <ItemCondition>X</ItemCondition>
            <ItemSubcondition>X</ItemSubcondition>
            <FulfillmentChannel>Merchant</FulfillmentChannel>
            <ShipsDomestically>X</ShipsDomestically>
            <ShippingTime>
              <Max>X</Max>
            </ShippingTime>
            <SellerPositiveFeedbackRating>X</SellerPositiveFeedbackRating>
          </Qualifiers>
          <NumberOfOfferListingsConsidered>4</NumberOfOfferListingsConsidered>
          <SellerFeedbackCount>X</SellerFeedbackCount>
          <Price>
            <LandedPrice>
              <CurrencyCode>X</CurrencyCode>
              <Amount>X</Amount>
            </LandedPrice>
            <ListingPrice>
              <CurrencyCode>X</CurrencyCode>
              <Amount>X</Amount>
            </ListingPrice>
            <Shipping>
              <CurrencyCode>X</CurrencyCode>
              <Amount>X</Amount>
            </Shipping>
          </Price>
          <MultipleOffersAtLowestPrice>X</MultipleOffersAtLowestPrice>
        </LowestOfferListing>
        <LowestOfferListing>
          <Qualifiers>
            <ItemCondition>X</ItemCondition>
            <ItemSubcondition>X</ItemSubcondition>
            <FulfillmentChannel>X</FulfillmentChannel>
            <ShipsDomestically>X</ShipsDomestically>
            <ShippingTime>
              <Max>X</Max>
            </ShippingTime>
            <SellerPositiveFeedbackRating>X</SellerPositiveFeedbackRating>
          </Qualifiers>
          <NumberOfOfferListingsConsidered>1</NumberOfOfferListingsConsidered>
          <SellerFeedbackCount>X</SellerFeedbackCount>
          <Price>
            <LandedPrice>
              <CurrencyCode>X</CurrencyCode>
              <Amount>X</Amount>
            </LandedPrice>
            <ListingPrice>
              <CurrencyCode>X</CurrencyCode>
              <Amount>X</Amount>
            </ListingPrice>
            <Shipping>
              <CurrencyCode>X</CurrencyCode>
              <Amount>X</Amount>
            </Shipping>
          </Price>
          <MultipleOffersAtLowestPrice>X</MultipleOffersAtLowestPrice>
        </LowestOfferListing>
      </LowestOfferListings>
    </Product>
  </GetLowestOfferListingsForSKUResult>
  <ResponseMetadata>
    <RequestId>X</RequestId>
  </ResponseMetadata>
</GetLowestOfferListingsForSKUResponse>

和myList看起来像： 

myList = ['10032590',
'10043503',
'10047539',
'10055404',
'10058424'...
]

使用下面的第一个答案我收到以下错误消息：

TypeError：不可用类型：'list'

我相信相关的代码是： 

def xml_to_dict(self, xml):
    doc = lh.fromstring(xml)
    d = {}
    for product in doc.xpath('.//product'):
        sku = product.xpath('.//sellersku/text()')
        amount = product.xpath('./descendant::amount[1]/text()')
        d[sku] = amount
    return d

1 个解决方案

解决方案1
 6 已采纳  2013-01-17 17:26:04

d={}
for product in doc.xpath('.//product'):
    sku = product.xpath('.//sellersku/text()')[0]
    price = product.xpath('./descendant::amount[1]/text()')
    if price: # if theres a possibility of sku missing replace with:
              # "if price and sku"
              #
              # if you have duplicate sku's and you don't want them overwritten 
              # add "and sku not in d" check
        d[sku]= price[0]

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