（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。
