错误：PrettyPrinter超出了函数范围

Question

此代码会打开一个CSV，读取并打印＆＃39;标题后的第一行。行。我使用pprint来获取字典的输出。但是，即使使用print（），我的代码也不会打印任何内容。我哪里错了？

import csv

from datetime import datetime
from pprint import PrettyPrinter 

def print_first_point(filename):
"""
This function prints and returns the first data point (second row) from
a csv file that includes a header row.
"""
# print city name for reference
city = filename.split('-')[0].split('/')[-1]
print('\nCity: {}'.format(city))

with open(filename, 'r') as f_in:
     trip_reader = csv.DictReader(f_in)

    def first_trip (trip_reader):
        reader = csv.DictReader (trip_reader)
        first = next (reader)
        return first

    pp = pprint.PrettyPrinter(indent=4)
    pp.pprint(first_trip)