使用Python 3更新CSV文件（添加/删除行） [英] Updating CSV file (add/remove rows) with Python 3

问题描述

每天都有人，

我有一个Raspberry Pi系统，它跟踪各种用户检出的工具。我已经设置它，使得系统的扫描执行时，用户签入，以及当他们签出。通过比较两次扫描，我可以确定是否已经采用/返回了刀具。但是，我还有一个Log.csv文件，它跟踪哪些工具当前检出。我可以添加到这个日志当一个工具签出（这里没有问题），但我有麻烦在工具返回时删除该行。

I've got a Raspberry Pi system which keeps track of tools being checked out by various users. I've set it up such that a scan of the system is performed when a user checks in, as well as when they check out. By comparing the two scans, I can determine whether a tool has been taken/returned. However, I also have a Log.csv file which keeps track of which tools are currently checked out. I'm able to add to this log when a tool is checked out (no problems here), but I'm having trouble removing that row when the tool is returned.

我搜索了SO为这个解决方案，但还没有找到任何具体的。根据我的理解，您无法从CSV文件中删除单个行？我将不得不重写该文件，并且该特定的行被省略？

I've searched SO for a solution to this, but haven't found anything concrete. From what I understand, you can't remove a single row from a CSV file? I would have to re-write the file, with that particular row being omitted?

这里是我到目前为止，包括添加和删除行Log.csv文件：

Here's what I have so far, including both adding and remove rows on the Log.csv file:

with open('Log.csv', 'a+') as f:
    reader = csv.reader(f)
    if tools_taken not in reader:
        csv.writer(open('Log.csv', 'a+')).writerow([tools_taken])

with open('Log.csv', 'a+') as f:
    reader = csv.reader(f)
    if tools_returned in reader:
        ???

请记住，上述代码已简化，以保持简洁。我想如果tools_returned在读者行是太含糊。我可以将其更改为：

Bear in mind that the above code is simplified to keep it succinct. I'm thinking that the 'if tools_returned in reader' line is too vague. I might change it to:

for row in reader:
    for field in row:
        if field == tools_taken:
            ???

我在正确的轨道上吗？任何输入都会非常感谢！

Am I on the right track? Any input here would be very much appreciated!

推荐答案

我不认为 csv 是这里的正确结构。你想能够查找一个给定的工具，找出它的 tools_taken 是True还是改变它的 tools_taken 或者从文件中删除工具，或者向文件中添加工具，是吗？

I don't think csv is the right structure here. You want to be able to look up a given tool, find out whether its tools_taken is True, or change its tools_taken, or remove a tool from the file, or add a tool to the file, right?

这是数据库的用途，例如 shelve ：

That's what a database is for, such as shelve:

import contextlib
import shelve

tools = shelve.open('Log.db', 'c', writeback=True)
with contextlib.closing(tools):
    # Add a tool
    tools['hammer'] = {'name': 'Hammer', 'owner': 'Joe', 'tools_taken': False}
    # Check if a tool is taken
    if tools['screwdriver']['tools_taken']:
        print('The screwdriver is taken!')
    # Change a tool's taken status:
    tools['screwdriver']['tools_taken'] = True
    # Remove a tool
    del tools['jackhammer']

换句话说，你可以只是一个 dict 这种情况下，充满 dict s），但它会自动持续运行。

In other words, you can just it just like a dict (in this case, full of dicts), but it's automatically persistent across runs.

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