为什么csv.DictReader跳过空行?

问题描述

即使设置了 restval ，似乎 csv.DictReader 也会跳过空行.使用以下内容，将跳过输入文件中的空行:

It seems that csv.DictReader skips empty lines, even when restval is set. Using the following, empty lines in the input file are skipped:

import csv
CSV_FIELDS = ("field1", "field2", "field3")
for row in csv.DictReader(open("f"), fieldnames=CSV_FIELDS, restval=""):
    if not row or not row[CSV_FIELDS[0]]:
        sys.exit("never reached, why?")

文件 f 在哪里:

1,2,3


a,b,c

推荐答案

在csv.DictReader类中:

    # unlike the basic reader, we prefer not to return blanks,
    # because we will typically wind up with a dict full of None
    # values
    while row == []:
        row = self.reader.next()

因此跳过了空行.如果您不想跳过空行，则可以使用 csv.reader .

So empty rows are skipped.If you don't want to skip empty lines, you could instead use csv.reader.

另一个选择是将 csv.DictReader 子类化:

Another option is to subclass csv.DictReader:

import csv
CSV_FIELDS = ("field1", "field2", "field3")

class MyDictReader(csv.DictReader):
    def next(self):
        if self.line_num == 0:
            # Used only for its side effect.
            self.fieldnames
        row = self.reader.next()
        self.line_num = self.reader.line_num

        d = dict(zip(self.fieldnames, row))
        lf = len(self.fieldnames)
        lr = len(row)
        if lf < lr:
            d[self.restkey] = row[lf:]
        elif lf > lr:
            for key in self.fieldnames[lr:]:
                d[key] = self.restval
        return d

for row in MyDictReader(open("f", 'rb'), fieldnames=CSV_FIELDS, restval=""):
    print(row)

收益

{'field2': '2', 'field3': '3', 'field1': '1'}
{'field2': '', 'field3': '', 'field1': ''}
{'field2': '', 'field3': '', 'field1': ''}
{'field2': 'b', 'field3': 'c', 'field1': 'a'}

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