Question

使用以下数据，使用代码段，我收到以下错误。你能帮我解决这个问题吗？我是python的初学者。数据：

"Id","Title","Body","Tags"
"Id1","Tit,le1","Body1","Ta,gs1"
"Id","Title","Body","Ta,2gs"

代码：

#!/usr/bin/python 
import csv,sys
if len(sys.argv) <> 3:
print >>sys.stderr, 'Wrong number of arguments. This tool will print first n records from a comma separated CSV file.' 
print >>sys.stderr, 'Usage:' 
print >>sys.stderr, '       python', sys.argv[0], '<file> <number-of-lines>'
sys.exit(1)

fileName = sys.argv[1]
n = int(sys.argv[2])

i = 0 
out = csv.writer(sys.stdout, delimiter=',', quotechar='"', quoting=csv.QUOTE_NONNUMERIC)

ret = []


def read_csv(file_path, has_header = True):
    with open(file_path) as f:
        if has_header: f.readline()
        data = []
        for line in f:
            line = line.strip().split("\",\"")
            data.append([x for x in line])
    return data


ret = read_csv(fileName)
target = []
train = []
target = [x[2] for x in ret]
train = [x[1] for x in ret]

错误：

    target = [x[2] for x in ret]
IndexError: list index out of range

Answer 1

您正在混合file.readline()并将文件对象用作可迭代的。不要那样做。请改用next()。

您还应该使用csv.reader()模块来读取数据，不要重新发明这个轮子。 csv模块可以处理引用的CSV值，并且在任何情况下都可以更好地嵌入值中的分隔符：

import csv

def read_csv(file_path, has_header=True):
    with open(file_path, 'rb') as f:
        reader = csv.reader(f)
        if has_header: next(reader, None)
        return list(reader)

最后但并非最不重要的是，您可以使用zip()来转置行和列：

ret = read_csv(fileName)
target, train = zip(*ret)[1:3]  # just the 2nd and 3rd columns

此处zip()将停在不足够列的第一行，至少可以避免您看到的异常。

如果某些行中缺少列，请改用itertools.izip_longest()（Python 3中为itertools.zip_longest()）：

from itertools import izip_longest

ret = read_csv(fileName)
target, train = izip_longest(*ret)[1:3]  # just the 2nd and 3rd columns

默认设置是用None替换丢失的列;如果您需要使用其他值，请将fillvalue参数传递给izip_longest()：

target, train = izip_longest(*ret, fillvalue=0)[1:3]  # just the 2nd and 3rd columns

在python中读取csv文件

1 个答案: