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第六章、FOR、IF和while

纽二 2022-02-28 阅读 144

(一)if 语句

if语句

people = 20
cats = 30
dogs = 15


if people < cats:
    print("Too many cats,The world is doomed")
if people > cats:
    print("Not mangy cats! The world is saved!")


if people < dogs:
    print("The world is drooled on!")

if people >dogs:
    print("The world is dry!")


dogs +=5

if people >=dogs:
    print("People are greater than or equal to dogs.") 

if people <=dogs:
    print("People are less than or equal to dogs.")


if people ==dogs:
    print("People are dogs.")

运行的结果:

Too many cats,The world is doomed
The world is dry!
People are greater than or equal to dogs.
People are less than or equal to dogs.
People are dogs.
[Finished in 1.4s]

上面有if代码块,if代码块创建了一个分支;按照python语法要求必须缩进4个空格,这是告诉python创建了新的代码块。如果添加上elif,else等。

Else和if

people = 30
cars =40
trucks = 15


if cars > people:
    print("We should take the cars.")
elif cars < people:
    print("We should not take the cars.")
else:
    print("We cat't decide.")

if trucks >cars:
    print("That too many trucks!")
elif trucks < cars:
    print("Maybe we could take the trucks!")
else:
    print("We still can't decide!")

if people > trucks:
    print("Alright, let's just take the trucks.")
else:
    print('Fine, let\'s  stay home then')

运行的结果:

We should take the cars.
Maybe we could take the trucks!
Alright, let's just take the trucks.
[Finished in 132ms]

注意:if-elif-else语句,python从顶部开始,只运行第一个True的代码块,其他的就不运行了;所以如果需要每个条件都需要做出判断的情况下,可以使用多个if条件,像上面的多个if语句。

IF嵌套使用

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

door = input(">")

if door =='1':
    print("There's a giant bear here eating a cheese cake.")
    print("What do you do?")
    print("1,Take the  cake.")
    print("2,Scream at the bear.")

    bear = input(">")

    if bear =='1':
        print("The bear eats your face off.Good job!")
    elif bear =='2':
        print("The bear eats your legs off.Good job!")
    else:
        print(f"Well,doing {bear} is probably better.")
        print("Bear runs away.")

elif door=='2':
    print("You stare into the endless abyss at Cthulhu's retina.")
    print("1,Blueberries.")
    print("2,Yellow jacket clothespins.")
    print("3,Understanding revolvers yelling melodies.")

    insanity = input(">")

    if insanity =='1'or insanity =='2':
        print("Your body survies powered by a mind of jello.")
        print("Good job!")

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

运行的结果:

You enter a dark room with two doors.
Do you go through door #1 or door #2?
>1
There's a giant bear here eating a cheese cake.
What do you do?
1,Take the  cake.
2,Scream at the bear.
>2
The bear eats your legs off.Good job!

sublime text无法完成交互,使用终端解决交互的问题。

(二)FOR语句

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
for number in the_count:
    print(f"This is count {number}")

#same as above
for fruit in fruits:
    print(f"A fruit of type {fruit}")

# also we can go through mixed lists too
# notice we have to use {} since we don't know what's in it
for i in change:
    print(f"I got {i}")

#we can also build lists, first start with an empty one
elements = []

# then use the range function to do 0 to 5 counts
for i in range(0,6):
    print(f"Adding {i} to the list.")
# append is a function that lists understand
    elements.append(i)

# now we can print them out too
for i in elements:
    print(f"Elements was: {i}")

运行的结果:

This is count 1
This is count 2
This is count 3
This is count 4
This is count 5
A fruit of type apples
A fruit of type oranges
A fruit of type pears
A fruit of type apricots
I got 1
I got pennies
I got 2
I got dimes
I got 3
I got quarters
Adding 0 to the list.
Adding 1 to the list.
Adding 2 to the list.
Adding 3 to the list.
Adding 4 to the list.
Adding 5 to the list.
Elements was: 0
Elements was: 1
Elements was: 2
Elements was: 3
Elements was: 4
Elements was: 5
[Finished in 116ms]

注意for 语句的遍历,以及函数range的用法,注意点。

(三)while语句

i = 0
numbers = []

while i < 6:
    print(f"At the top i is {i} ")
    numbers.append(i)

    i +=1
    print("Numbers now:",numbers)
    print(f"At the bottom i is {i}")
print("The numbers:")
for i in numbers:
    print(i)

运行的结果:

At the top i is 0 
Numbers now: [0]
At the bottom i is 1
At the top i is 1 
Numbers now: [0, 1]
At the bottom i is 2
At the top i is 2 
Numbers now: [0, 1, 2]
At the bottom i is 3
At the top i is 3 
Numbers now: [0, 1, 2, 3]
At the bottom i is 4
At the top i is 4 
Numbers now: [0, 1, 2, 3, 4]
At the bottom i is 5
At the top i is 5 
Numbers now: [0, 1, 2, 3, 4, 5]
At the bottom i is 6
The numbers:
0
1
2
3
4
5
[Finished in 133ms]

分支和函数

from sys import exit
def gold_room():
    print("This room is full of gold. How much do you take?")


    choice = input('>')
    if '0' in choice or '1' in choice:
        how_much = int(choice)
    else:
        dead("Man,learn to type a number.")

    if how_much <50:
        print("Nice,you're not greedy,you win!")
        exit(0)
     else:
        dead("You greedy bastard!")
def bear_room():
    print('There is a bear here.')
    print("The bear has a bunch of honey.")
    print("The fat bear is in front of another door.")
    print("How are you going to move the  bear?")
    bear_moved =False



    while True:
        choice = input('>')

        if choice =='take honey':
            dead("The bear looks at you then slaps your face")
        elif choice =="taunt bear" and not bear_moved:
            print("The bear has moved from the door.")
            print("You can go through it now.")
            bear_moved = True

        elif choice=="taunt bear" and bear_moved:
            dead("The bear gets pissed off and chews your leg.")

        elif choice=="open door" and bear_moved:
            gold_room()
        else:
            print("I got no idea what that means.")

def cthulhu_room():
    print("Here you see the great evil Cthulhu")
    print("He,it,whatever strats at you and you go insane")
    print("Do you flee your life or eat your head?")
    choice = input(">")

    if 'flee' in choice:
        strat()
    elif 'head' in choice:
        dead("Well that was tasty!")
    else:
        cthulhu_room()

def dead():
    print(why,"Good job!")
    exit(0)

def start():
    print("You are in a dark room.")
    print("There is a door to your right and left.")
    print("Which one do you take?")


    choice = input('>')

    if choice =='left':
        bear_room()
    elif choice =='right':
        cthulhu_room()

    else:
        dead("You stumble around the room until you starve.")

start()

运行的结果:

You are in a dark room.
There is a door to your right and left.
Which one do you take?
>left
There is a bear here.
The bear has a bunch of honey.
The fat bear is in front of another door.
How are you going to move the  bear?
>taunt bear
The bear has moved from the door.
You can go through it now.
>open door
This room is full of gold. How much do you take?
>1000
You greedy bastard! Good job!

理解这个游戏中的逻辑。

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