什麼是 zip 物件？

Python 程式面試題實作練習

Kirill Smirnov

Data Science Consultant, Altran

定義

zip：將多個可疊代物件合併為單一可疊代物件。

多個可疊代物件的集合

$\text{e}_\text{i}$：來自可疊代物件的元素

定義

zip：將多個可疊代物件合併為單一可疊代物件。

將多個可疊代物件合併成 zip 物件

$\text{e}_\text{i}$：來自可疊代物件的元素

定義

zip：將多個可疊代物件合併為單一可疊代物件。

疊代 zip 物件

$\text{e}_\text{i}$：來自可疊代物件的元素

範例

title = 'TMNT'
villains = ['Shredder', 'Krang', 'Bebop', 'Rocksteady']
turtles = {
    'Raphael': 'Sai', 'Michelangelo': 'Nunchaku',
    'Leonardo': 'Twin katana', 'Donatello': 'Bo'
}

result = zip(title, villains, turtles)
print(result)

<zip object at 0x7f37bab6e608>

走訪 zip 物件

result = zip(title, villains, turtles)

for item in result:
    print(item)

('T', 'Shredder', 'Raphael')
('M', 'Krang', 'Michelangelo')
('N', 'Bebop', 'Leonardo')
('T', 'Rocksteady', 'Donatello')

回傳 tuple 清單

result = zip(title, villains, turtles)

tuples = list(result)
print(tuples)

[
    ('T', 'Shredder', 'Raphael'), ('M', 'Krang', 'Michelangelo'),
    ('N', 'Bebop', 'Leonardo'), ('T', 'Rocksteady', 'Donatello')
]

將 zip 物件當作 Iterator

result = zip(title, villains, turtles)

next(result)

('T', 'Shredder', 'Raphael')

next(result)

('M', 'Krang', 'Michelangelo')

next(result)

('N', 'Bebop', 'Leonardo')

next(result)

('T', 'Rocksteady', 'Donatello')

next(result)

StopIteration

zip 物件會被消耗

result = zip(title, villains, turtles)

for item in result:
    print(item)

('T', 'Shredder', 'Raphael')
('M', 'Krang', 'Michelangelo')
('N', 'Bebop', 'Leonardo')
('T', 'Rocksteady', 'Donatello')

zip 物件會被消耗

result = zip(title, villains, turtles)

for item in result:
    print(item)

('T', 'Shredder', 'Raphael')
('M', 'Krang', 'Michelangelo')
...

for item in result:
    print(item)

# nothing

result = zip(title, villains, turtles)

tuples = list(result)
print(tuples)

[
    ('T', 'Shredder', 'Raphael'),
    ('M', 'Krang', 'Michelangelo'),
    ('N', 'Bebop', 'Leonardo'),
    ('T', 'Rocksteady', 'Donatello')
]

『zip』物件會被消耗

result = zip(title, villains, turtles)

for item in result:
    print(item)

('T', 'Shredder', 'Raphael')
('M', 'Krang', 'Michelangelo')
...

for item in result:
    print(item)

# nothing

result = zip(title, villains, turtles)

tuples = list(result)
print(tuples)

[
    ('T', 'Shredder', 'Raphael'),
    ...

tuples = list(result)
print(tuples)

[]

可疊代物件長度不一致

title = 'TMNT'
villains = ['Shredder', 'Krang', 'Bebop', 'Rocksteady']
turtles = {
    'Raphael': 'Sai', 'Michelangelo': 'Nunchaku',
    'Leonardo': 'Twin katana', 'Donatello': 'Bo'
}

可疊代物件長度不一致

title = 'Teenage Mutant Ninja Turtles'
villains = ['Shredder', 'Krang', 'Bebop', 'Rocksteady']
turtles = {
    'Raphael': 'Sai', 'Michelangelo': 'Nunchaku',
    'Leonardo': 'Twin katana', 'Donatello': 'Bo'
}

result = zip(title, villains, turtles)

走訪『zip』物件

result = zip(title, villains, turtles)

for item in result:
    print(item)

('T', 'Shredder', 'Raphael')
('e', 'Krang', 'Michelangelo')
('e', 'Bebop', 'Leonardo')
('n', 'Rocksteady', 'Donatello')

反向操作

turtle_masks = [
    ('Raphael', 'red'), ('Michelangelo', 'orange'),
    ('Leonardo', 'blue'), ('Donatello', 'purple')
]

result = zip(*turtle_masks)
print(result)

[
    ('Raphael', 'Michelangelo', 'Leonardo', 'Donatello'),
    ('red', 'orange', 'blue', 'purple')
]

tuple 長度不一致

turtle_masks = [
    ('Raphael', 'red'), ('Michelangelo', 'orange'),
    ('Leonardo', 'blue', 'cyan'), ('Donatello', 'purple', 'magenta')
]

result = zip(*turtle_masks)
print(result)

[
    ('Raphael', 'Michelangelo', 'Leonardo', 'Donatello'),
    ('red', 'orange', 'blue', 'purple')
]

與字典的關係

可以用 zip 物件建立字典

keys = ['movie', 'year', 'director']
values = [
    ['Forest Gump', 'Goodfellas', 'Se7en'],
    [1994, 1990, 1995],
    ['R.Zemeckis', 'M.Scorsese', 'D.Fincher']
]

movies = dict(zip(keys, values))

print(movies)

{
    'director': [
        'R.Zemeckis',
        'M.Scorsese',
        'D.Fincher'
    ], 
    'movie': [
        'Forest Gump',
        'Goodfellas',
        'Se7en'
    ],
    'year': [1994, 1990, 1995]
}

建立 DataFrame

import pandas as pd

df_movies = pd.DataFrame(movies)

print(df_movies)

          director        movie  year
0  Robert Zemeckis  Forest Gump  1994
1  Martin Scorsese   Goodfellas  1990
2    David Fincher        Se7en  1995

list()

建立 DataFrame

import pandas as pd

df_movies = pd.DataFrame(movies)

print(df_movies)

          director        movie  year
0  Robert Zemeckis  Forest Gump  1994
1  Martin Scorsese   Goodfellas  1990
2    David Fincher        Se7en  1995

list() $\rightarrow$ zip()

建立 DataFrame

import pandas as pd

df_movies = pd.DataFrame(movies)

print(df_movies)

          director        movie  year
0  Robert Zemeckis  Forest Gump  1994
1  Martin Scorsese   Goodfellas  1990
2    David Fincher        Se7en  1995

list() $\rightarrow$ zip() $\rightarrow$ dict()

建立 DataFrame

import pandas as pd

df_movies = pd.DataFrame(movies)

print(df_movies)

          director        movie  year
0  Robert Zemeckis  Forest Gump  1994
1  Martin Scorsese   Goodfellas  1990
2    David Fincher        Se7en  1995

list() $\rightarrow$ zip() $\rightarrow$ dict() $\rightarrow$ DataFrame()

一起來練習吧！

Python 程式面試題實作練習