Advanced filtering

在這個教程中我們將看下如何使用F這個對象進(jìn)行高級的主機過濾衣吠，讓我們從初始化nornir開始然后
看下inventory:

from nornir import InitNornir
from nornir.core.filter import F

nr = InitNornir(config_file="advanced_filtering/config.yaml")

---
%cat advanced_filtering/inventory/hosts.yaml

cat:
    groups:
        - terrestrial
        - mammal
    data:
        domestic: true
        diet: omnivore
        additional_data:
            lifespan: 17
            famous_members:
                - garfield
                - felix
                - grumpy

bat:
    groups:
        - terrestrial
        - mammal
    data:
        domestic: false
        fly: true
        diet: carnivore
        additional_data:
            lifespan: 15
            famous_members:
                - batman
                - count chocula
                - nosferatu

eagle:
    groups:
        - terrestrial
        - bird
    data:
        domestic: false
        diet: carnivore
        additional_data:
            lifespan: 50
            famous_members:
                - thorondor
                - sam

canary:
    groups:
        - terrestrial
        - bird
    data:
        domestic: true
        diet: herbivore
        additional_data:
            lifespan: 15
            famous_members:
                - tweetie

caterpillaer:
    groups:
        - terrestrial
        - invertebrate
    data:
        domestic: false
        diet: herbivore
        additional_data:
            lifespan: 1
            famous_members:
                - Hookah-Smoking

octopus:
    groups:
        - marine
        - invertebrate
    data:
        domestic: false
        diet: carnivore
        additional_data:
            lifespan: 1
            famous_members:
                - sharktopus

%cat advanced_filtering/inventory/groups.yaml

---
mammal:
    data:
        reproduction: birth
        fly: false

bird:
    data:
        reproduction: eggs
        fly: true

invertebrate:
    data:
        reproduction: mitosis
        fly: false

terrestrial: {}
marine: {}

你可以看到我們已經(jīng)準(zhǔn)備了一些擁有不同屬性的動物袖订。F對象可以讓你訪問魔法方法，這些魔法方法都是兩個下劃線和魔法方法的名稱組成的灾梦。例如玫坛，如果你想檢查一個列表里是否包含指定的元素可以通過__contains魔法方法掂僵。讓我們通過這個特性獲取所有屬于鳥類的動物:

birds = nr.filter(F(groups__contains="bird"))
print(birds.inventory.hosts.keys())

輸出:
dict_keys(['eagle', 'canary'])

我們還可以通過~來進(jìn)行取反:

birds = nr.filter(~F(groups__contains="bird"))
print(birds.inventory.hosts.keys())

輸出:
dict_keys(['cat', 'bat', 'caterpillaer', 'octopus'])

我們還可以復(fù)合F對象通過符號&和|來單獨執(zhí)行且和或的操作:

domestic_or_bird = nr.filter(F(groups__contains="bird") | F(domestic=True))
print(domestic_or_bird.inventory.hosts.keys())

輸出:
dict_keys(['cat', 'eagle', 'canary'])


domestic_mammals = nr.filter(F(groups__contains="mammal") & F(domestic=True))
print(domestic_mammals.inventory.hosts.keys())

輸出:
dict_keys(['cat'])

如你所想，你可以組合所有的符號:

flying_not_carnivore = nr.filter(F(fly=True) & ~F(diet="carnivore"))
print(flying_not_carnivore.inventory.hosts.keys())

輸出:
dict_keys(['canary'])

你還可以通過訪問魔法方法的方式訪問嵌套的數(shù)據(jù)授嘀，通過在你想訪問的數(shù)據(jù)前加兩個下劃線。你可以根據(jù)需求繼續(xù)建造甚至訪問嵌套數(shù)據(jù)的魔法方法锣险。例如蹄皱，讓我們獲取那些壽命大于等于15的動物：

long_lived = nr.filter(F(additional_data__lifespan__ge=15))
print(long_lived.inventory.hosts.keys())

輸出:
dict_keys(['cat', 'bat', 'eagle', 'canary'])

還有兩個"特殊服務(wù)"來幫助你處理lists览闰，any和all。這些方法可以讓你發(fā)送一個列表的元素來獲取那些包含一個或包含全部元素的對象巷折。例如:

marine_and_invertebrates = nr.filter(F(groups__all=["marine", "invertebrate"]))
print(marine_and_invertebrates.inventory.hosts.keys())

輸出:
dict_keys(['octopus'])


bird_or_invertebrates = nr.filter(F(groups__any=["bird", "invertebrate"]))
print(bird_or_invertebrates.inventory.hosts.keys())

輸出:
dict_keys(['eagle', 'canary', 'caterpillaer', 'octopus'])