从Flask视图创建和下载CSV文件

Question

我试图允许用户下载包含其操作定义的数据的CSV文件。该文件不存在，它是动态创建的。如何在Flask中做到这一点？

Answer 1

使用生成数据csv.writer并传输响应。使用StringIO写入内存缓冲区，而不是生成中间文件。

import csv
from datetime import datetime
from io import StringIO
from flask import Flask
from werkzeug.wrappers import Response

app = Flask(__name__)

# example data, this could come from wherever you are storing logs
log = [
    ('login', datetime(2015, 1, 10, 5, 30)),
    ('deposit', datetime(2015, 1, 10, 5, 35)),
    ('order', datetime(2015, 1, 10, 5, 50)),
    ('withdraw', datetime(2015, 1, 10, 6, 10)),
    ('logout', datetime(2015, 1, 10, 6, 15))
]

@app.route('/')
def download_log():
    def generate():
        data = StringIO()
        w = csv.writer(data)

        # write header
        w.writerow(('action', 'timestamp'))
        yield data.getvalue()
        data.seek(0)
        data.truncate(0)

        # write each log item
        for item in log:
            w.writerow((
                item[0],
                item[1].isoformat()  # format datetime as string
            ))
            yield data.getvalue()
            data.seek(0)
            data.truncate(0)

    # stream the response as the data is generated
    response = Response(generate(), mimetype='text/csv')
    # add a filename
    response.headers.set("Content-Disposition", "attachment", filename="log.csv")
    return response

如果该generate函数需要从current中获取信息request，则应使用修饰stream_with_context，否则您将收到“在外部请求上下文中工作”错误。其他所有内容保持不变。

from flask import stream_with context

@stream_with_context
def generate():
    ...