比较两个列表并按字段搜索，Python

Question

我希望比较两个文件，然后生成特定的输出：

1) 下面是用户名文本文件的内容（这里存储了用户最近看过的电影）

    Sci-Fi,Out of the Silent Planet
    Sci-Fi,Solaris
    Romance, When Harry met Sally

2) 以下是films.txt 文件的内容，该文件存储了程序中可供用户使用的所有电影

0,Genre, Title, Rating, Likes
1,Sci-Fi,Out of the Silent Planet, PG,3
2,Sci-Fi,Solaris, PG,0
3,Sci-Fi,Star Trek, PG,0
4,Sci-Fi,Cosmos, PG,0
5,Drama, The English Patient, 15,0
6,Drama, Benhur, PG,0
7,Drama, The Pursuit of Happiness, 12, 0
8,Drama, The Thin Red Line, 18,0
9,Romance, When Harry met Sally, 12, 0
10,Romance, You've got mail, 12, 0
11,Romance, Last Tango in Paris, 18, 0
12,Romance, Casablanca, 12, 0

我需要的输出示例：用户当前观看了两部科幻片和一部爱情片。因此，输出应按类型搜索电影文本文件（标识 SCI-FI 和 ROMANCE），并应在films.txt 文件中列出用户尚未观看的电影。在这种情况下

3,Sci-Fi,Star Trek, PG,0
4,Sci-Fi,Cosmos, PG,0
10,Romance, You've got mail, 12, 0
11,Romance, Last Tango in Paris, 18, 0
12,Romance, Casablanca, 12, 0

我有以下代码尝试执行上述操作，但它产生的输出不正确：

def viewrecs(username):
   #set the username variable to the text file -to use it in the next bit
   username = (username + ".txt")
   #open the username file that stores latest viewings
   with open(username,"r") as f:
      #open the csv file reader for the username file
          fReader=csv.reader(f)
          #for each row in the fReader
          for row in fReader:
             #set the genre variable to the row[0], in which row[0] is all the genres (column 1 in username file)
             genre=row[0]
             #next, open the films file
             with open("films.txt","r") as films:
                #open the csv reader for this file (filmsReader as opposed to fReader)
                filmsReader=csv.reader(films)
                #for each row in the films file
                for row in filmsReader:
                   #and for each field in the row 
                   for field in row:
                      #print(field)
                      #print(genre)
                      #print(field[0])
                      if genre in field and row[2] not in fReader:
                         print(row)

输出（不需要的）：

['1', 'Sci-Fi', 'Out of the Silent Planet', ' PG', '3']
['2', 'Sci-Fi', 'Solaris', ' PG', '0']
['3', 'Sci-Fi', 'Star Trek', ' PG', '0']
['4', 'Sci-Fi', 'Cosmos', ' PG', '0']

我不想要重写或新的解决方案，但最好是修复上述解决方案的逻辑进展......

@gipsy - 您的解决方案似乎几乎奏效了。我用过：

def viewrecs(username):

  #set the username variable to the text file -to use it in the next bit
  username = (username + ".txt")
  #open the username file that stores latest viewings
  lookup_set = set()
  with open(username,"r") as f:
    #open the csv file reader for the username file
    fReader=csv.reader(f)
    #for each row in the fReader
    for row in fReader:
      genre = row[1]
      name = row[2]
      lookup_set.add('%s-%s' % (genre, name))
  with open("films.txt","r") as films:
    filmsReader=csv.reader(films)
    #for each row in the films file
    for row in filmsReader:
      genre = row[1]
      name = row[2]
      lookup_key = '%s-%s' % (genre, name)
      if lookup_key not in lookup_set:
        print(row)

输出如下：它正在打印所有电影中不在第一组中的所有行，而不仅仅是基于第一组中基于 GENRE 的行：

['0', 'Genre', ' Title', ' Rating', ' Likes']
['3', 'Sci-Fi', 'Star Trek', ' PG', ' 0']
['4', 'Sci-Fi', 'Cosmos', ' PG', ' 0']
['5', 'Drama', ' The English Patient', ' 15', ' 0']
['6', 'Drama', ' Benhur', ' PG', ' 0']
['7', 'Drama', ' The Pursuit of Happiness', ' 12', ' 0']
['8', 'Drama', ' The Thin Red Line', ' 18', ' 0']
['10', 'Romance', " You've got mail", ' 12', ' 0']
['11', 'Romance', ' Last Tango in Paris', ' 18', ' 0']
['12', 'Romance', ' Casablanca', ' 12', ' 0']

注意：为简单起见，我将第一组的格式更改为与所有电影条目相同：

1,Sci-Fi,Out of the Silent Planet, PG
2,Sci-Fi,Solaris, PG

Answer 1

如何使用集合和单独的列表来过滤未看过的适当类型的电影？我们甚至可以为此滥用字典的keys 和values：

def parse_file (file):
    return map(lambda x: [w.strip() for w in x.split(',')], open(file).read().split('\n'))

def movies_to_see ():
    seen = {film[0]: film[1] for film in parse_file('seen.txt')}
    films = parse_file('films.txt')
    to_see = []

    for film in films:
        if film[1] in seen.keys() and film[2] not in seen.values():
            to_see.append(film)
    return to_see 

Answer 2

使用str.split()和str.join()函数的解决方案：

# change file paths with your actual ones
with open('./text_files/user.txt', 'r') as userfile:
    viewed = userfile.read().split('\n')
    viewed_genders = set(g.split(',')[0] for g in viewed)

with open('./text_files/films.txt', 'r') as filmsfile:
    films = filmsfile.read().split('\n')
    not_viewed = [f for f in films
                  if f.split(',')[1] in viewed_genders and ','.join(f.split(',')[1:3]) not in viewed]

print('\n'.join(not_viewed))

输出：

3,Sci-Fi,Star Trek, PG,0
4,Sci-Fi,Cosmos, PG,0
10,Romance, You've got mail, 12, 0
11,Romance, Last Tango in Paris, 18, 0
12,Romance, Casablanca, 12, 0

Answer 3

好的，通过第一个文件构建一个集合，以 Genre + name 作为条目。

现在遍历第二个文件并在上面创建的集合中查找 Genre+ 名称的条目，如果不存在则打印出来。

回家后，我可以输入一些代码。

正如我所承诺的，我的代码如下：

def viewrecs(username):
  #set the username variable to the text file -to use it in the next bit
  username = (username + ".txt")
  # In this set we will collect the unique combinations of genre and name
  genre_name_lookup_set = set()
  # In this set we will collect the unique genres 
  genre_lookup_set = set()
  with open(username,"r") as f:
    #open the csv file reader for the username file
    fReader=csv.reader(f)
    #for each row in the fReader
    for row in fReader:
      genre = row[0]
      name = row[1]
      # Add the genre name combination to this set, duplicates will be taken care automatically as set won't allow dupes  
      genre_name_lookup_set.add('%s-%s' % (genre, name))
      # Add genre to this set
      genre_lookup_set.add(genre)
  with open("films.txt","r") as films:
    filmsReader=csv.reader(films)
    #for each row in the films file
    for row in filmsReader:
      genre = row[1]
      name = row[2]
      # Build a lookup key using genre and name, example:Sci-Fi-Solaris
      lookup_key = '%s-%s' % (genre, name)
      if lookup_key not in genre_name_lookup_set and genre in genre_lookup_set:
        print(row)