# WARM UP
def count_words(filename: str) -> int:
    """Return the number of words in the text file filename"""
    count = 0
    with open(filename) as myFile:
        for line in myFile:
            count += len(line.split())
    return count

count_words("words.txt")

11

# WARM UP
import csv

def oldest_student(filename: str) -> str:
    """Return the name of the oldest student in the csv file filename"""
    with open(filename) as myFile:
        csvFile = csv.DictReader(myFile)
        
        oldestName = ""
        oldestAge = -1
        
        for student in csvFile:
            if int(student["Age"]) > oldestAge:
                oldestAge = int(student["Age"])
                oldestName = student["Name"]
    return oldestName

oldest_student("Students.csv")

'Lily'

import csv
def filter_city(inFile: str, outFile: str, cityName: str) -> None:
    """Write a new file to outFile that has the information from
    inFile about only the city called cityName"""
    with open(inFile) as ifh:
        inputCSV = csv.DictReader(ifh)
        fieldnames = list(inputCSV.fieldnames or [])
        
        with open(outFile, "w") as ofh:
            outputCSV = csv.DictWriter(ofh, fieldnames)
            outputCSV.writeheader()
            
            for line in inputCSV:
                if line["City"] == cityName:
                    outputCSV.writerow(line)
    
filter_city("City Data.csv", "waterloo.csv", "Waterloo")