import csv
from pathlib import Path

path = Path("reading.csv")

def get_summary(path):
    input_path = Path(path)
    with input_path.open(encoding="utf-8", newline="") as file:
        rows = csv.DictReader(file)
        pages = []
        missing = 0
        for row in rows:
            if row["pages"] == "":
                missing += 1
            else:
                pages.append(int(row["pages"]))
        count = len(pages)
        total = sum(pages)
        average = total / count if count else None
        return count, total, average, missing

count, total, average, missing = get_summary("reading.csv")
print(f"件数は{count}件です")
print(f"合計は{total}ページです")
if average is None:
    print("平均を計算できません")
else:
    print(f"平均は{average:.1f}ページです")
print(f"空欄は{missing}件です")