在python中迭代特定的csv行将输出一个空白文件

python新手-我正在尝试格式化一组我发送的非常粗略的csv，以便我可以将它们放入一个漂亮的postgres表中进行查询和分析。为了做到这一点，我首先用CSV.Wrror清理它们，删除每个行的空白行和双引号。我的代码是这样的：

import os
import csv
import glob
from itertools import islice

files = glob.glob('/Users/foo/bar/*.csv')

# Loop through all of the csv's  
for file in files:
    # Get the filename from the path
    outfile = os.path.basename(file)

    with open(file, 'rb') as inp, open('/Users/foo/baz/' + outfile, 'wb') as out:

        reader = csv.reader(inp)
        writer = csv.writer(out)
        for row in reader:
            if row:
                writer.writerow(row)
        out.close() 

它工作得非常好，完全符合我的要求。输出csv看起来很棒。接下来，我尝试从新清理的csv文件的开头和结尾切掉一定数量的包含完全不必要垃圾的行（省略前8行和最后2行）。出于我确实无法确定的原因，这部分代码的csv输出（缩进与前面的“with”块相同）完全为空：

with open('/Users/foo/baz/' + outfile, 'rb') as inp2, open('/Users/foo/qux/' + outfile, 'wb') as out2:
    writer2 = csv.writer(out2)
    reader2 = csv.reader(inp2)
    row_count = sum(1 for row in reader2)
    last_line_index = row_count - 3 
    for row in islice(reader2, 7, last_line_index):
            writer2.writerow(row)
    out2.close()

我知道，由于我的“with”用法，每个块末尾的close（）是多余的-我在查看后尝试了这种方法。我还尝试将第二个“with”块放入另一个文件中，并在运行第一个“with”块后运行该文件，但仍然无效。非常感谢你的帮助

此外，以下是整个文件：

import os
import csv
import glob
from itertools import islice

files = glob.glob('/Users/foo/bar/*.csv')

# Loop through all of the csv's  
for file in files:
    # Get the filename from the path
    outfile = os.path.basename(file)

    with open(file, 'rb') as inp, open('/Users/foo/baz/' + outfile, 'wb') as out:

        reader = csv.reader(inp)
        writer = csv.writer(out)
        for row in reader:
            if row:
                writer.writerow(row)
        out.close() 

    with open('/Users/foo/baz/' + outfile, 'rb') as inp2, open('/Users/foo/qux/' + outfile, 'wb') as out2:
        writer2 = csv.writer(out2)
        reader2 = csv.reader(inp2)
        row_count = sum(1 for row in reader2)
        last_line_index = row_count - 3 
        for row in islice(reader2, 7, last_line_index):
                writer2.writerow(row)
        out2.close()

谢谢

有罪的一方是

row_count = sum(1 for row in reader2)

它从

reader2

读取所有数据；现在，当您尝试

为islice中的行（reader2，7，last\u line\u index）

获取任何数据时

此外，您可能正在读取大量的空行，因为您以二进制方式打开文件；取而代之的是

with open('file.csv', newline='') as inf:
    rd = csv.reader(inf)

---

您可以像这样快速修复代码（正如@Hugh Bothwell所说，我用问题注释了这行代码，您已经从变量

reader2

读取了所有数据）：

---

这才是问题所在！加上一个快速！你太快了！。。。。。啊哈！我不知道这是一次交易！非常感谢您的快速响应！我很感激，伙计！您的解决方案也很完美，Hugh刚刚比我的收件箱快了一点：）

import os
import csv
import glob
from itertools import islice

files = glob.glob('/Users/foo/bar/*.csv')

# Loop through all of the csv's  
for file in files:
    # Get the filename from the path
    outfile = os.path.basename(file)

    with open(file, 'rb') as inp, open('/Users/foo/baz/' + outfile, 'wb') as out:

        reader = csv.reader(inp)
        writer = csv.writer(out)
        for row in reader:
            if row:
                writer.writerow(row)
        out.close() 

    with open('/Users/foo/baz/' + outfile, 'rb') as inp2, open('/Users/foo/qux/' + outfile, 'wb') as out2:
            writer2 = csv.writer(out2)
            reader2 = csv.reader(inp2)
            row_count = sum(1 for row in csv.reader(inp2)) #here you separately count the amount of rows without read the variable reader2
            last_line_index = row_count - 3 
            for row in islice(reader2, 7, last_line_index):
                    writer2.writerow(row)
            out2.close()