How do you split reading a large csv file into evenly-sized chunks in Python?

Question

In a basic I had the next process.

import csv
reader = csv.reader(open('huge_file.csv', 'rb'))

for line in reader:
    process_line(line)

See this related question. I want to send the process line every 100 rows, to implement batch sharding.

The problem about implementing the related answer is that csv object is unsubscriptable and can not use len.

>>> import csv
>>> reader = csv.reader(open('dataimport/tests/financial_sample.csv', 'rb'))
>>> len(reader)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: object of type '_csv.reader' has no len()
>>> reader[10:]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: '_csv.reader' object is unsubscriptable
>>> reader[10]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: '_csv.reader' object is unsubscriptable

How can I solve this?