python中向CSV写入多行数据

Question

I'm a noob trying to learn Python by scraping a website to track fund parameters. So far, the following code isolates and shows the data that I need,

from bs4 import BeautifulSoup
import requests

source = requests.get('https://www.fundaggregatorurl.com/path/to/fund').text
soup = BeautifulSoup(source, 'lxml')

# print(soup.prettify())

print("\n1Y growth rate vs S&P BSE 500 TRI\n")
# Pinpoints the 1Y growth rate of the scheme and the S&P BSE 500 TRI
for snippet in soup.find_all('div', class_='scheme_per_amt prcntreturn 1Y'):
    print(snippet.text.lstrip())

print("\nNAV, AUM and Expense Ratio\n")
# Pinpoints NAV, AUM and Expense Ratio
for snippet in soup.find_all('span', class_='amt'):
    print(snippet.text)

# Get the risk analysis data
source = requests.get('https://www.fundaggregatorurl.com/path/to/fund/riskanalysis').text
soup = BeautifulSoup(source, 'lxml')

print("\nRisk Ratios\n")
# Pinpoints NAV, AUM and Expense Ratio
for snippet in soup.find_all('div', class_='percentage'):
    split_data = snippet.text.split('vs')
    print(*split_data, sep=" ")

print()

This code shows the following data:

1Y growth rate vs S&P BSE 500 TRI

68.83%
50.85%

NAV, AUM and Expense Ratio

185.9414
2704.36
1.5%

Risk Ratios

19.76 17.95
0.89 0.93
0.77 0.72
0.17 0.14
4.59 2.32

How can I write this data to a CSV with the following headers?

Fund growth         Category Growth         Current NAV         AUM                 Expense Ratio           Fund std dev            Category std dev            Fund beta           Category beta           Fund Sharpe ratio           Category Sharpe ratio           Fund Treynor's ratio            Category Treynor's Ratio            Fund Jension's Alpha            Category Jension's Alpha
68.83%              50.85%                  185.9414            2704.36             1.5%                    19.76                   17.95                       0.89                0.93                    0.77                        0.72                            0.17                            0.14                                4.59                            2.32

This is for a single fund and I need to get this data for about 100 more funds. I will experiment more and any issues there are perhaps for another Q at a later time:) Since I'm a newbie, any other improvements and why you'd do those would also be appreciated!

Answer 1

Assemble the data for each fund in a list to easily write it out in CSV format using Python's builtin csv module :

import csv

funds = ['fund1', 'fund2']
# the header should match the number of data items
header = ['Fund growth', 'Category Growth', 'Current NAV', 'AUM']

with open('funds.csv', 'w', newline='') as csvfile:
    fund_writer = csv.writer(csvfile)
    fund_writer.writerow(header)
    for fund in funds:
        fund_data = []
        source = requests.get('https://www.fundaggregatorurl.com/path/to/' + fund).text
        soup = BeautifulSoup(source, 'lxml')

        for snippet in soup.find_all('div', class_='scheme_per_amt prcntreturn 1Y'):
            fund_data.append(snippet.text.lstrip())

        # do remaining parsing...

        fund_writer.writerow(fund_data)