Python3 在 tar 文件中处理 csv 文件

Question

我正在尝试处理包含在 tar.gz 文件中的 csv 文件，但在将正确的数据/对象传递给 csv 模块时遇到问题。

假设我有一个 tar.gz 文件，其中包含许多格式如下的 csv 文件。

1079,SAMPLE_A,GROUP,001,,2017/02/15 22:57:30
1041,SAMPLE_B,GROUP,023,,2017/02/15 22:57:26
1077,SAMPLE_C,GROUP,005,,2017/02/15 22:57:31
1079,SAMPLE_A,GROUP,128,,2017/02/15 22:57:38

我希望能够访问内存中的每个 csv 文件，而无需从 tar 文件中提取每个文件并将它们写入磁盘。例如:

import tarfile
import csv

tar = tarfile.open("tar-file.tar.gz")

for member in tar.getmembers():
    f = tar.extractfile(member).read()
    content = csv.reader(f)
    for row in content:
        print(row)
tar.close()

这会产生以下错误。

    for row in content:
_csv.Error: iterator should return strings, not int (did you open the file in text mode?)

我还尝试按照 csv 模块文档中的描述将 f 解析为字符串。

content = csv.reader([f])

上面产生了同样的错误。

我尝试将文件对象 f 解析为 ascii。

f = tar.extractfile(member).read().decode('ascii')

但这会迭代每个 csv 元素，而不是迭代包含元素列表的行。

['1']
['0']
['7']
['9']
['', '']
['S']
['A']
['M']
['P']
['L']
['E']
['_']
['A']
['', '']
['G']
['R']

剪断...

['2']
['0']
['1']
['7']
['/']
['0']
['2']
['/']
['1']
['5']
[' ']
['2']
['2']
[':']
['5']
['7']
[':']
['3']
['8']
[]
[]

尝试将 f 解析为 ascii 并将其作为字符串读取

f = tar.extractfile(member).read().decode('ascii')
content = csv.reader([f])

产生以下输出

    for row in content:
_csv.Error: new-line character seen in unquoted field - do you need to open the file in universal-newline mode?

为了演示不同的输出，我使用了以下代码。

import tarfile
import csv

tar = tarfile.open("tar-file.tar.gz")

for member in tar.getmembers():
    f = tar.extractfile(member).read()
    print(member.name)
    print('Raw :', type(f))
    print(f)
    print()
    f = f.decode('ascii')
    print('ASCII:', type(f))
    print(f)
tar.close()

这会产生以下输出。 (对于此示例，每个 csv 包含相同的数据)。

./raw_data/csv-file1.csv
Raw : <class 'bytes'>
b'1079,SAMPLE_A,GROUP,001,,2017/02/15 22:57:30\n1041,SAMPLE_B,GROUP,023,,2017/02/15 22:57:26\n1077,SAMPLE_C,GROUP,005,,2017/02/15 22:57:31\n1079,SAMPLE_A,GROUP,128,,2017/02/15 22:57:38\n\n'

ASCII: <class 'str'>
1079,SAMPLE_A,GROUP,001,,2017/02/15 22:57:30
1041,SAMPLE_B,GROUP,023,,2017/02/15 22:57:26
1077,SAMPLE_C,GROUP,005,,2017/02/15 22:57:31
1079,SAMPLE_A,GROUP,128,,2017/02/15 22:57:38


./raw_data/csv-file2.csv
Raw : <class 'bytes'>
b'1079,SAMPLE_A,GROUP,001,,2017/02/15 22:57:30\n1041,SAMPLE_B,GROUP,023,,2017/02/15 22:57:26\n1077,SAMPLE_C,GROUP,005,,2017/02/15 22:57:31\n1079,SAMPLE_A,GROUP,128,,2017/02/15 22:57:38\n\n'

ASCII: <class 'str'>
1079,SAMPLE_A,GROUP,001,,2017/02/15 22:57:30
1041,SAMPLE_B,GROUP,023,,2017/02/15 22:57:26
1077,SAMPLE_C,GROUP,005,,2017/02/15 22:57:31
1079,SAMPLE_A,GROUP,128,,2017/02/15 22:57:38


./raw_data/csv-file3.csv
Raw : <class 'bytes'>
b'1079,SAMPLE_A,GROUP,001,,2017/02/15 22:57:30\n1041,SAMPLE_B,GROUP,023,,2017/02/15 22:57:26\n1077,SAMPLE_C,GROUP,005,,2017/02/15 22:57:31\n1079,SAMPLE_A,GROUP,128,,2017/02/15 22:57:38\n\n'

ASCII: <class 'str'>
1079,SAMPLE_A,GROUP,001,,2017/02/15 22:57:30
1041,SAMPLE_B,GROUP,023,,2017/02/15 22:57:26
1077,SAMPLE_C,GROUP,005,,2017/02/15 22:57:31
1079,SAMPLE_A,GROUP,128,,2017/02/15 22:57:38

如何让 csv 模块正确读取 tar 模块提供的内存中的文件？谢谢。

Answer 1

您只需要使用 io.StringIO() 生成一个类似对象的文件供 csv 库使用。例如:

import tarfile
import csv
import io

with tarfile.open('input.rar') as tar:
    for member in tar:
        if member.isreg():      # Is it a regular file?
            print("{} - {} bytes".format(member.name, member.size))
            csv_file = io.StringIO(tar.extractfile(member).read().decode('ascii'))

            for row in csv.reader(csv_file):
                print(row)