如何将实时数据写入python中的csv文件 [英] how to write the real time data into csv file in python

问题描述

def event_handler_quote_update(message):
    # print(f"quote update {message}")
    global row_no
    global token
    global ltp
    global Date
    token = message['token']
    ltp =   message['ltp']
    Date = message['exchange_time_stamp']

我需要将上述实时运行数据写入csv文件，目前，我的python脚本不会执行任何操作来写入csv文件.

i need to write the above live running data into csv file currently my python script will not do anything writing the csv file.

当前它正在处理excel文件，但是在从不同的脚本读取相同的excel时遇到了问题，因此我打算将数据写入csv文件中，

currently it is working with excel file, but i am having issue while reading same excel from different script, so i am planning to write the data into csv file,

推荐答案

无需在 global 中声明所有这些内容.当 def 之外的变量需要从内部进行更改时， global 声明非常有用且必要.

There is no need to declare any of those things global. A global declaration is useful and necessary when there is a variable outside of your def which you need to change from inside.

要写入CSV数据，请使用 csv 库.

For writing CSV data, probably use the csv library.

import csv

# ...

def event_handler_quote_update(message):
    # print(f"quote update {message}")
    token = message['token']
    ltp   = message['ltp']
    date  = message['exchange_time_stamp']
    with open('results.csv', 'a+') as csvfile:
        writer = csv.writer(csvfile)
        writer.writerow([token, ltp, date])

如果有一种方法可以打开CSV文件以进行写入并实例化 writer 对象一次，那么只需在回调之外，然后简单地传入 writer ，那会好得多.code>作为 message 之后的第二个参数；不过，完成后，您将需要分别 close().

It would be a lot better if there was a way to open the CSV file for writing and instantiate the writer object just once, outside the callback, and simply pass in writer as the second argument after message; though then, you will need to close() it separately when you are done.

import csv

# ...

def event_handler_quote_update(message, writer):
    # print(f"quote update {message}")
    token = message['token']
    ltp   = message['ltp']
    date  = message['exchange_time_stamp']
    writer.writerow([token, ltp, date])

# ...

if __name__ == '__main__':
    # whatever else you have here
    csvfile = open('results.csv', 'w')
    writer = csv.writer(csvfile)

    # ... whatever else your program needs to do

    csvfile.close()

但是也许您无法控制回调的调用方式.那么也许您确实需要 writer 成为 def 中的 global .

But maybe you don't have control over how the callback gets called. Then maybe you do need writer to be global inside the def.

实际上不需要将每个字段都复制到一个单独的变量中；如果要提取很多字段，可能会切换到类似

There's no need really to copy each field into a separate variable; if there are a lot of fields you want to extract, probably switch to something like

        writer.writerow([message[x] for x in ('token', 'ltp', 'exchange_time_stamp')])

如果您需要使用另一种CSV格式的变体(例如制表符或分号分隔，或在顶部写一个标题等)，请参见上面的文档链接.

See the documentation link above if you need to use a different variant of CSV format, like tab or semicolon delimited, or write a header at the top, etc. It's all there.

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