Question

我已经嵌套了DictReader迭代器，但是我注意到for build in building中的for row in location在每次迭代后都没有重置import csv building = csv.DictReader(open('tblBuilding.csv', newline=''), delimiter=',', quotechar='"') purpose = csv.DictReader(open('tblPurpose.csv', newline=''), delimiter=',', quotechar='"') room = csv.DictReader(open('tblRoom.csv', newline=''), delimiter=',', quotechar='"') location = csv.DictReader(open('Locations.csv', newline=''), delimiter=',', quotechar='"') data, i = {}, 0 for row in location: result = {} for build in building: if row['Build'] == build['BuildingName']: result['BuildingID'] = build['BuildingID']，导致它只在第一次迭代后将它与构建中的最后一个对象进行比较。为什么不重置？

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Answer 1

它们不会重置，因为底层文件对象未重置。您可以将文件重新回到开头，但考虑到第一行是标题行，所以也跳过它：

building_file = open('tblBuilding.csv', newline='')
building = csv.DictReader(building_file, delimiter=',', quotechar='"')


for row in location:
    result = {}
    for build in building:
        if row['Build'] == build['BuildingName']:
            result['BuildingID'] = build['BuildingID']
    building_file.seek(0)  # rewind the underlying file object to the start again
    next(building)  # skip header row

然而，您不应该首先在上嵌套嵌套的CSV文件。在处理位置之前，将建筑信息存储在字典中

with open('tblBuilding.csv', newline='') as building_file: building = csv.DictReader(building_file, delimiter=',', quotechar='"') buildings = {b['BuildingName']: b['BuildingID'] for b in building}

buildings词典现在将BuildingName映射到BuildingID值。现在，您可以在O（1）常数时间内查找建筑物，而不必遍历每个位置的所有CSV行：

for row in location: result = {} building_id = buildings.get(row['Build']) if building_id: result['BuildingID'] = building_id

嵌套的DictReaders没有重置

1 个答案: