DataFrame 数据选取和过滤

允许这样的操作的

pd.read_csv('imdb.txt')
  .sort(columns='year')
  .filter(lambda x: x['year']>1990)   # <---this is missing in Pandas
  .to_csv('filtered.csv')

等同于

df = pd.read_csv('imdb.txt').sort(columns='year')
df[df['year']>1990].to_csv('filtered.csv')

# 或者这样写
pd.read_csv('imdb.txt')
  .sort(columns='year')
  .[lambda x: x['year']>1990]
  .to_csv('filtered.csv')