Question

我希望在原始文本文件中识别重复项，一旦识别出重复项，我想在创建新的CSV文件时忽略它。

raw_file_reader = csv.DictReader(open(raw_file), delimiter='|')

保存在我的原始文件中是一个简单的.txt文件

with open('file') as f:
  seen = set()
  for line in f:
      line_lower = line.lower()
      if line_lower in seen:
          print(line)
      else:
          seen.add(line_lower)

我可以使用集合

找到重复项

for row in raw_file_reader:
            if ('Symbol' in row):
                symbol = row['Symbol']
            elif ('SYMBOL' in row):
                symbol = row['SYMBOL']
            else:
                raise exception

            if symbol not in symbol_lookup:
                continue

我只是不确定在转换为csv文件之前如何实际忽略重复项。

Answer 1

我会使用csv库来执行此操作。此外，还有一种内置的枚举项目的方法。所以，让我们使用它。

import csv
with open("in.txt","r") as fi, open("out.csv","w") as fo:
    writer = csv.writer(fo, lineterminator='\n')
    writer.writerows(enumerate(set(fi.read().split("|"))))

Answer 2

您可以按照以下步骤将所有条目存储在一个集合中来删除重复项：

import csv

seen = set()
output = []

source_file = "file.csv"

with open(source_file, 'rb') as f_input:
    csv_input = csv.reader(f_input, delimiter='|')

    for row in csv_input:
        if tuple(row) not in seen:
            output.append(row)
            seen.add(tuple(row))

with open(source_file, 'wb') as f_output:        
    csv_output = csv.writer(f_output)
    csv_output.writerows(output)

给你一个输出文件：

20100830,TECD,1500,4300,N
20100830,TECH,100,100,N
20100830,TECUA,100,391,N
20100830,TEF,1300,1300,N
20100830,TEG,900,1900,N

这通过将每个整行转换为元组来实现，然后可以将其存储为集合。这样可以直接测试重复行。

在Python 2.7.12上测试

Answer 3

您可以简单地创建一个自定义迭代器，它将返回删除重复项的原始文件行：

class Dedup:
    def __init__(self, fd):
        self.fd = fd       # store the original file object
        self.seen = set()  # initialize an empty set for lines
    def __next__(self):        # the iterator method
        while True:
            line = next(self.fd)
            if not line in self.seen:
                self.seen.add(line)
                return line
            # print("DUP>", line.strip(), "<") # uncomment for tests
    def __iter__(self):        # make the iterator compatible Python 2 and 3
        return self
    def next(self):
        return self.__next__()
    def __enter__(self):       # make it a context manager supporting with
        return self
    def __exit__(self, typ, value, traceback):
        self.fd.close()        # cleanup

然后您可以简单地创建您的DictReader：

with Dedup(open(raw_file)) as fd:
   reader = csv.DictReader(fd, delimiter='|')
   for row in reader:
        # process each now unique row...

但要注意！这将要求所有行都存储在集合中，这意味着原始文件必须适合内存。

在转换为CSV

3 个答案: