Problem with Generator

[palladium]

Hi all

I am trying to learn about generators. The code below is showing some strange behaviours (the aim is to calculate the average raised Amt for each company in round "a"):

techcruncher.csv:

Output:
permalink,company,numEmps,category,city,state,fundedDate,raisedAmt,raisedCurrency,round
digg,Digg,60,web,San Francisco,CA,01-Dec-06,8500000,USD,b
digg,Digg,60,web,San Francisco,CA,01-Oct-05,2800000,USD,a
facebook,Facebook,450,web,Palo Alto,CA,01-Sep-04,500000,USD,angel
facebook,Facebook,450,web,Palo Alto,CA,01-May-05,12700000,USD,a
photobucket,Photobucket,60,web,Palo Alto,CA,01-Mar-05,3000000,USD,a

file_name = "techcruncher.csv"
lines = (line for line in open(file_name))
list_line = (s.rstrip().split(",") for s in lines)
cols = next(list_line)
company_dicts = (dict(zip(cols,data)) for data in list_line)
unique_companies = (
    company_dict["company"]
    for company_dict in company_dicts
    if company_dict["round"] == ("a".lower())
)
number_of_companies = len(list(unique_companies))
print(number_of_companies)

I get the output below, which is what I expect.

Output:
PS D:\python> python generatorlearn.py
3

However, when I change the code to this:

file_name = "techcruncher.csv"
lines = (line for line in open(file_name))
list_line = (s.rstrip().split(",") for s in lines)
cols = next(list_line)
company_dicts = (dict(zip(cols,data)) for data in list_line)
funding = (
    int(company_dict["raisedAmt"])
    for company_dict in company_dicts
    if company_dict["round"] == ('A'.lower())
)
total_series_a = sum(funding)
print(total_series_a)
unique_companies = (
    company_dict["company"]
    for company_dict in company_dicts
    if company_dict["round"] == ("a".lower())
)
number_of_companies = len(list(unique_companies))
print(number_of_companies)

(new lines are 6-12 inclusive), I get the following output:

Output:
PS D:\python> python generatorlearn.py
18500000
0

Somehow the generator unique_companies do not seem to work anymore.
Would appreciate if someone could explain why is this the case.
Thanks in advance!