【Python爬虫】-笨办法学 Python 习题 27-34

习题 27:  记住逻辑关系

and 与

or 或

not 非

 != (not equal) 不等于

== (equal) 等于

>= (greater-than-equal) 大于等于

<= (less-than-equal) 小于等于

True 真

 False 假

习题 28:布尔表达式练习

print(True and True)

print(False and True)

print(1==1and2==1)

print("test"=="test")

print(1==1or2!=1)

print(True and1==1)

print(False and0!=0)

print(True or1==1)

print("test"=="testing")

print(1!=0and2==1)

print("test"!="testing")

print("test"==1)

print(not(True and False))

print(not(1==1and0!=1))

print(not(10==1or1000==1000))#False

print(not(1!=10or3==4))#False

print(not("testing"=="testing"and"Zed"=="Cool Guy"))

print(1==1and not("testing"==1or1==0))

print("chunky"=="bacon"and not(3==4or3==3))

print(3==3and not("testing"=="testing"or"Python"=="Fun"))#False

习题 29:  如果(if)

people =20

cats =30

dogs=15

ifpeople < cats:

print("Too many cats! The world is doomed!")

ifpeople > cats:

print("Not many cats! The world is saved!")

ifpeople

print("The world is drooled on!")

ifpeople >dogs:

print("The world is dry!")

dogs+=5

ifpeople >=dogs:

print("People are greater than or equal to dogs.")

ifpeople <=dogs:

print("People are less than or equal to dogs.")

ifpeople ==dogs:

print("People are dogs.")

习题 30: Else  和 If

people =30

cars =40

buses =15

ifcars > people:

print("We should take the cars.")

elifcars < people:

print("We should not take the cars.")

else:

print("We can't decide.")

ifbuses > cars:

print("That's too many buses.")

elifbuses < cars:

print("Maybe we could take the buses.")

else:

print("We still can't decide.")

ifpeople > buses:

print("Alright, let's just take the buses.")

else:

print("Fine, let's stay home then.")

习题 31:  作出决定

print("You enter a dark room with two doors. Do you go through door #1 or door #2?")

door =input("> ")

ifdoor =="1":

print("There's a giant bear here eating a cheese cake. What do you do?")

print("1.Take the cake.")

print("2.Scream at the bear.")

bear =input("> ")

ifbear =="1":

print("The bear eats your face off. Good job!")

elifbear =="2":

print("The bear eats your legs off. Good job.")

else:

print("Well, doing %s is probably better. Bear runs away."% bear)

elifdoor =="2":

print("You stare into the endless abyss at Cthulhu'sretina.")

print("1. Blueberries.")

print("2. Yellow jacket clothespins.")

print("3. Understanding revolvers yelling melodies.")

insanity =input("> ")

ifinsanity =="1"orinsanity =="2":

print("Your body survives powered by a mind of jello. Good job!")

else:

print("The insanity rots your eyes into a pool of muck. Good job!")

else:

print("You stumble around and fall on a knife and die. Good job!")

习题 32:  循环和列表

the_count = [1,2,3,4,5]

fruits = ["apples","oranges","pears","apricots"]

change = [1,"pennies",2,"dimes",3,"quarters"]

# this first kind of for-loop goes through a list

fornumberinthe_count:

print("This is count %d"% number)

# same as above

forfruitinfruits:

print("A fruit of type: %s"% fruit)

# also we can go through mixed lists too

# notice we have to use %r since we don't know what's in it

foriinchange:

print("I got %r"% i)

# we can also build lists, first start with an empty one

elements = []

# then use the range function to do 0 to 5 counts

foriinrange(0,6):

print("Adding %d to the list."% i)

# append is a function that lists understand

elements.append(i)

# now we can print them out too

foriinelements:

print("Element was: %d"% i)

习题 33: While循环

i =0

numbers = []

whilei <6:

print("At the top i is %d"% i)

numbers.append(i)

i = i +1

print("Numbers now: ",numbers)

print("At the bottom i is %d"% i)

print("The numbers:")

fornuminnumbers:

print(num)

习题 34:  访问列表的元素

animals = ['bear','python','peacock','kangaroo','whale','platypus']

print(animals[0])

print(animals[1])

print(animals[2])

print(animals[3])

print(animals[4])

print(animals[5])