之前看爬虫的时候，看到这里就断了，一直不太理解这2个的区别。

今天重新看，也借助了这位哥们的方法，把结果打印出来，我大概知道了这2者的区别。

http://www.cnblogs.com/chensimin1990/p/6725803.html

 

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from urllib.request import urlopenfrom bs4 import BeautifulSouphtml = urlopen("http://www.pythonscraping.com/pages/page3.html")bs_obj = BeautifulSoup(html,'html.parser')# name_list = bs_obj.find_all("span", {"class":"green"})#for name in name_list:#    print(name.get_text())  # file = open('test.txt','w')# content = ''for child in bs_obj.find("table",{
   "id":"giftList"}).descendants:    print(child)

代码是这样的

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Item TitleDescriptionCostImageItem TitleItem TitleDescriptionDescriptionCostCostImageImageVegetable BasketThis vegetable basket is the perfect gift for your health conscious (or overweight) friends!Now with super-colorful bell peppers!$15.00Vegetable BasketVegetable BasketThis vegetable basket is the perfect gift for your health conscious (or overweight) friends!Now with super-colorful bell peppers!This vegetable basket is the perfect gift for your health conscious (or overweight) friends!Now with super-colorful bell peppers!Now with super-colorful bell peppers!$15.00$15.00Russian Nesting DollsHand-painted by trained monkeys, these exquisite dolls are priceless! And by "priceless," we mean "extremely expensive"! 8 entire dolls per set! Octuple the presents!$10,000.52Russian Nesting DollsRussian Nesting DollsHand-painted by trained monkeys, these exquisite dolls are priceless! And by "priceless," we mean "extremely expensive"! 8 entire dolls per set! Octuple the presents!Hand-painted by trained monkeys, these exquisite dolls are priceless! And by "priceless," we mean "extremely expensive"!8 entire dolls per set! Octuple the presents!8 entire dolls per set! Octuple the presents!$10,000.52$10,000.52Fish PaintingIf something seems fishy about this painting, it's because it's a fish! Also hand-painted by trained monkeys!$10,005.00Fish PaintingFish PaintingIf something seems fishy about this painting, it's because it's a fish! Also hand-painted by trained monkeys!If something seems fishy about this painting, it's because it's a fish!Also hand-painted by trained monkeys!Also hand-painted by trained monkeys!$10,005.00$10,005.00Dead ParrotThis is an ex-parrot! Or maybe he's only resting?$0.50Dead ParrotDead ParrotThis is an ex-parrot! Or maybe he's only resting?This is an ex-parrot!Or maybe he's only resting?Or maybe he's only resting?$0.50$0.50Mystery BoxIf you love suprises, this mystery box is for you! Do not place on light-colored surfaces. May cause oil staining. Keep your friends guessing!$1.50Mystery BoxMystery BoxIf you love suprises, this mystery box is for you! Do not place on light-colored surfaces. May cause oil staining. Keep your friends guessing!If you love suprises, this mystery box is for you! Do not place on light-colored surfaces. May cause oil staining.Keep your friends guessing!Keep your friends guessing!$1.50$1.50

这是结果

 

用children的函数（？不知道为什么叫函数，感觉没有括号，明明是字段啊...）

from urllib.request import urlopenfrom bs4 import BeautifulSouphtml = urlopen("http://www.pythonscraping.com/pages/page3.html")bs_obj = BeautifulSoup(html,'html.parser')# name_list = bs_obj.find_all("span", {"class":"green"})#for name in name_list:#    print(name.get_text())  # file = open('test.txt','w')# content = ''for child in bs_obj.find("table",{
   "id":"giftList"}).children:    print(child)

结果是这样的：

Item TitleDescriptionCostImageVegetable BasketThis vegetable basket is the perfect gift for your health conscious (or overweight) friends!Now with super-colorful bell peppers!$15.00Russian Nesting DollsHand-painted by trained monkeys, these exquisite dolls are priceless! And by "priceless," we mean "extremely expensive"! 8 entire dolls per set! Octuple the presents!$10,000.52Fish PaintingIf something seems fishy about this painting, it's because it's a fish! Also hand-painted by trained monkeys!$10,005.00Dead ParrotThis is an ex-parrot! Or maybe he's only resting?$0.50Mystery BoxIf you love suprises, this mystery box is for you! Do not place on light-colored surfaces. May cause oil staining. Keep your friends guessing!$1.50

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到说明的时候：

1、chidlren并不是只返回子代的第一层，而是到没有子代的那一层，也就是说会穿透所有的，这个我以前以为是descendants干的事。

2、那descendants还留着干嘛呢？

是这么一个作用，他对每一个子代都会遍历一边他所有的后代。

如果我们打个比方：

a

-a1

--a11

--a12

--a13

---a131

----a1311

如果用children，其实就是原样返回，如果用descendants的话，他会在a13的时候返回一次a1311，a131的时候又返回一次a1311。

另外

for child in bs_obj.find("table",{"id":"giftList"}).children 和 

for child in bs_obj.find("table",{"id":"giftList"})是等价的，想想也知道，这个更符合一般人的直觉。