FastAPI – return contents of csv file as plain text

Question

Wondering if anyone can help me out please.

In FastAPI I want to set up an endpoint which returns the contents of a generated csv file as plain text. I don’t want the file to be downloaded.

I’ve tried the following which works just fine however a file download is always initiated.

  @app.get('/hosts/last_hour')
        def hosts_last_hour():
            epoch_start=time.mktime(datetime.now().timetuple())-3600
            epoch_end=time.mktime(datetime.now().timetuple())
            process_hosts(epoch_start,epoch_end)
            
            def iterate_csv(epoch_start):
                with open(f'output/hosts_traffic_{int(epoch_start)}.csv',mode='rb') as csv_file:
                    yield from csv_file

            response = StreamingResponse(iterate_csv(epoch_start), media_type="text/csv")
            return(response)

I need the contents of the file to be sent in the response body as text/csv (don’t want a downloaded to be initiated and don’t want the response in json format). Any ideas how to achieve this?

Thanks in advance.

José

Asked By: José Oliveira

||

Source

Answer 1

This will be easy using pandas:

Juast read the csv into a DataFrame using pd.read_csv and then turn the DataFrame into a dict using the to_dict() function.

Do note that pandas DataFrames can cause memory issues.

import pandas as pd
 
@app.get('/hosts/last_hour')
def hosts_last_hour():
   df_data = pd.read_csv("SampleCSVFile_11kb.csv")
   dict_data = df_data.to_dict()
   return dict_data

If you don’t want to use pandas then do this:

import csv
import json

@app.get('/hosts/last_hour')
def hosts_last_hour():
    data_dict = []
 
    with open("data.csv", encoding = 'utf-8') as csv_file_handler:
        csv_reader = csv.DictReader(csv_file_handler)
        for rows in csv_reader:
            data_dict.append(rows)

    return json.dumps(data_dict)

Answered By: Lars K.

Answer 2

In case anyone is looking for a similar solution, here’s what worked for me (see this answer for more details):

# 1 MB chunks    
CHUNK_SIZE = 1024 * 1024 
    
    @app.get('/hosts/')
        
        async def hosts():
            tenant=TENANT
            # Get data for the last hour
            epoch_start=time.mktime(datetime.now().timetuple())-MAX_QUERY_PERIOD
            epoch_end=time.mktime(datetime.now().timetuple())
    
            process_hosts(epoch_start,epoch_end)
            
            async def iter_file():
                async with aiofiles.open(f'output/hosts_traffic_{int(epoch_start)}.csv',mode='rb') as csv_file:
                    while chunk := await csv_file.read(CHUNK_SIZE):
                        yield chunk
            
            headers = {'Content-Disposition': 'inline'}
            response = StreamingResponse(iter_file(), media_type="text/csv",headers=headers)
    
            return response

Thanks!

Answered By: José Oliveira

FastAPI – return contents of csv file as plain text

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