Python基础（下）

 

第二周知识点总结¶

In [30]:

from random import choice
from random import randrange
from random import seed
from random import random

 

1、随机选择¶

（1）choice¶

In [4]:

# choice

doors = ['A', 'B', 'C']
# Randomly returns one of 'A', 'B' or 'C'
choice(doors)

Out[4]:

'A'

 

（2）randange¶

In [12]:

#rand

a=randrange(4)
print(list(range(4)))
print(a)

 

[0, 1, 2, 3]
3

In [28]:

# 固定每次随机的数   seed()

seed(100)   #如果给了seed值，后面的randrange每次运行选择的结果是一样的
a=randrange(20)
print(a)

 

4

In [42]:

# 用法示例

doors = ['A', 'B', 'C']
# 3 possible outcomes
first_chosen_door = doors.pop(randrange(3))
first_chosen_door, doors

Out[42]:

('B', ['A', 'C'])

 

（3）random¶

In [33]:

# random() 为0-1之间随机的数
a=random()
print(a)

 

0.17474750209982115

 

(4)randint¶

左闭右闭区间

In [ ]:

 

 

2、输入语句判断¶

In [34]:

while True:
    try:
        nb_of_games = int(input('How many games should I simulate? '))
        if nb_of_games <= 0:
            raise ValueError
        print('Ok, will do!')
        break
    except ValueError:
        print('Your input is incorrect, try again.')

 

How many games should I simulate? 12
Ok, will do!

In [35]:

while True:
    try:
        nb_of_games = int(input('How many games should I simulate? '))
        print('Ok, will do!')
        break
    except ValueError:
        print('Your input is incorrect, try again.')

 

How many games should I simulate? 12
Ok, will do!

In [43]:

# 示例

def set_simulation():
    while True:
        try:
            nb_of_games =\
                    int(input('How many games should I simulate? '))
            if nb_of_games <= 0:
                raise ValueError
            break
        except ValueError:
            print('Your input is incorrect, try again.')
    while True:
        contestant_switches = input('Should the contestant switch? ')
        if contestant_switches.istitle():
            contestant_switches = contestant_switches.lower()
        if contestant_switches in {'yes', 'y'}:
            contestant_switches = True
            print('I keep in mind you want to switch.')
            break
        if contestant_switches.lower() in {'no', 'n'}:
            contestant_switches = False
            print("I keep in mind you don't want to switch.")
            break
        print('Your input is incorrect, try again.')
    return nb_of_games, contestant_switches

set_simulation()

 

How many games should I simulate? 23
Should the contestant switch? 23
Your input is incorrect, try again.
Should the contestant switch? 23
Your input is incorrect, try again.
Should the contestant switch? y
I keep in mind you want to switch.

Out[43]:

(23, True)

 

3、一些对str的操作¶

In [37]:

# 是否以大写字母开头。   .istitle()

'Y'.istitle()
'Yes'.istitle()
'Yes_'.istitle()
'Yes_12_'.istitle()
'yes'.istitle()
'yEs'.istitle()
'Yes, by all means, yes!'.istitle()
'Yes, By All Means, Yes!'.istitle()

Out[37]:

True

In [41]:

# 把所有大写字母转为小写。    .lower()

'Yes, BY all means, yes!'.lower()

Out[41]:

'yes, by all means, yes!'

 

4、格式化输出¶

 

（1）f¶

In [49]:

x = 10
u = 4.5
v = 10
print(f'x is equal to {x}.'
      'That is not all: '
      f'{u} divided by {v} equals {u / v}.'
     )

 

x is equal to {x}. That is not all: 4.5 divided by 10 equals 0.45.

In [51]:

x = 123 / 321 
print(f'{x}')
print(f'{x:.0f}')
print(f'{x:.1f}')
print(f'{x:.2f}')
print(f'{x:.3f}')
print(f'{x:.4f}')
print(f'{x:.30f}')

 

0.38317757009345793
0
0.4
0.38
0.383
0.3832
0.383177570093457930955338497370

 

5、函数¶

（1）函数赋值¶

In [45]:

# x and y are parameters without default values,
# u and v are parameters without default values
def f(x, y, u=10, v=20):
    print(x, y, u, v)

# 2 positional arguments
f(1, 2)     #若未给u和v赋值，则默认为u=10, v=20
# 3 positional arguments
f(1, 2, 4)
# 4 positional arguments
f(1, 2, 3, 4)
# 1 positional argument, 2 keyword arguments
f(1, v=4, y=2)
# 3 keyword arguments
f(u=3, y=2, x=1)

 

1 2 10 20
1 2 4 20
1 2 3 4
1 2 10 4
1 2 3 20

 

（2）函数应用¶

In [46]:

# 函数使用举例：

#超过给定数量隐藏

def simulate(nb_of_games_to_display=3):
    for i in range(nb_of_games):
        if i < nb_of_games_to_display:
            print('Display all details of game number', i)
        elif i == nb_of_games_to_display:
            print('...')
            
nb_of_games = 2
simulate()
print()

nb_of_games = 3
simulate()
print()

nb_of_games = 4
simulate()

 

Display all details of game number 0
Display all details of game number 1

Display all details of game number 0
Display all details of game number 1
Display all details of game number 2

Display all details of game number 0
Display all details of game number 1
Display all details of game number 2
...

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