Python —循环分支语句
## 分支结构 -- if语句
```python
import getpass
username = input ('请输入用户名')
#password = input('请输入密码:') 明文
password = getpass.getpass('请输入密码：') #密文
if username == 'admin' and password == '123456':
print('欢迎使用本系统')# 缩进4个空格
print('开始运行APP')
else:
print('用户名或密码错误！')
print('今天天气真好')# 不受if-else 控制
```
## elif
```python
"""
f(x) = 5x + 3 (x < -1 )
2x - 1 (-1 <= x <= 1)
3x - 5 (x > 1)
"""
x = float(input('x = '))
if x < -1:
y = 5 * x + 3
elif x <= 1:
y = 2 * x - 1
else:
y = 3 * x -5
print('y =',y)
```
百分制转换成等级制 90以上A 80至90 B 70至80 C 60至70 D 其余是E
```python
score = float(input('请输入成绩'))
if score < 60:
print('成绩为E')
elif score < 70:
print('成绩为D')
elif score < 80:
print('成绩为C')
elif score < 90:
print('成绩为B')
else:
print('成绩为A')
```
下面这种嵌套的if...else 的写法是我们不推荐使用的，因为官方的建议是扁平优于嵌套
```python
score = float(input('请输入成绩'))
if score >= 90:
print('A')
else:
if score >= 80:
print('B')
else:
if score >= 70:
print('C')
else:
if score >= 60:
print('D')
else:
print('E')
```
掷骰子 1.
随机数random[0,1）
```python
import random
print( random.random())
```
```python
from random import random ,randint #从random中导入random
from math import pi , sqrt #从math中导入pi, sqrt
print(random())
print(random() * 200 -100)#[-100,100)
print(randint(1,6))#随机生成[1,6]的随机数
```
```python
from random import randint
r = randint(1,6)
if r == 1:
print('a')
elif r == 2:
print('b')
elif r == 3:
print('c')
elif r == 4:
print('d')
elif r == 5:
print('e')
else:
print('f')
```
1.顺序结构
2.分支结构
3.循环结构
## 循环结构
```python
from random import randint
f1 = f2 = f3 = f4 = f5 = f6 = 0
"""
f1 = 0
f2 = 0
f3 = 0
f4 = 0
f5 = 0
f6 = 0
"""
for x in range(60000): #执行60000次
r = randint(1,6)
if r == 1:
f1 += 1
elif r == 2:
f2 += 1
elif r == 3:
f3 += 1
elif r == 4:
f4 += 1
elif r == 5:
f5 += 1
else:
f6 += 1
print('1点摇出了%d次' % f1 )
print('2点摇出了%d次' % f2 )
print('3点摇出了%d次' % f3 )
print('4点摇出了%d次' % f4 )
print('5点摇出了%d次' % f5 )
print('6点摇出了%d次' % f6 )
```
pip install pycodestyle 检查工具
url统一资源定位符
```python
for x in range(1000): # x表示从0至 999 _同样是变量，默认不用
print('hello world')
# print('hello world! \n' * 1000) 同样效果
```
```python
\ 转义字符
\n 换行
```
```python
print(12,'12',sep = ':') # 中间以：分隔
```
12:12
```python
import time
for num in range(10):
print(num,'hello, world',sep=':')
time.sleep(1)# 间隔一秒
```
0:hello, world
1:hello, world
2:hello, world
3:hello, world
4:hello, world
5:hello, world
6:hello, world
7:hello, world
8:hello, world
9:hello, world
1 到 100求和
```python
my_sum = 0
for a in range(1,101):
my_sum += a
print(my_sum)
```
5050
```python
my_sum = 0
for a in range(1,101):
if a % 2 == 0:
my_sum += a
else:
pass # 跳过，else可省略，
print(my_sum)
```
2550
```python
my_sum = 0
for a in range(2,101,2):
my_sum += a
print(my_sum)
```
2550
1至100间 3或5的倍数 之和
```python
my_sum = 0
for x in range(101):
if x % 3 ==0 or x % 5 == 0:
my_sum += x
print(my_sum)
```
2418
## while 语句
```python
num = 0
while num < 10:
print('hello, world')
num += 1
```
hello, world
hello, world
hello, world
hello, world
hello, world
hello, world
hello, world
hello, world
hello, world
hello, world
```python
my_sum = 0
num = 0
while num < 101:
if num % 3 == 0 or num % 5 == 0:
my_sum += num
num += 1
print(my_sum)
```
猜数字，计算机随机出个数，人来猜，猜错了提示猜的过大或过小，猜对结束，猜错7次以上，智商捉急
```python
import random
num = 1
r = random.randint(1,100)
x = int(input('请输入1-100中的任意数字'))
while x != r:
if x > r:
x = int(input('您输入的数字偏大，请重新输入'))
else:
x = int(input('您输入的数字偏小,请重新输入'))
num += 1
if num > 7:
print('您的智商真着急')
print('恭喜您猜对了')
```
```python
from random import randint
answer + randint(1,100)
counter = 0
while True:
your_answer = int(int('请输入'))
counter += 1
if your_answer < answer:
print('大一点')
elif your_answer > answer:
print('小一点')
else:
print('恭喜您猜对了')
break
if counter > 7:
print('智商捉急')
```
# ### 复杂小乌龟
#
# In[6]:
import turtle
turtle.bgcolor('black')
turtle.pencolor('red')
turtle.fillcolor('red')
turtle.begin_fill()
turtle.pensize(width=8)
turtle.forward(300)
turtle.left(120)
turtle.forward(300)
turtle.left(120)
turtle.forward(300)
turtle.right(120)
turtle.end_fill()
turtle.pencolor('white')
for _ in range(60):
turtle.right(1)
turtle.forward(3)
turtle.pencolor('red')
turtle.begin_fill()
turtle.right(60)
turtle.forward(300)
turtle.right(120)
turtle.forward(300)
turtle.right(120)
turtle.forward(300)
turtle.right(60)
turtle.end_fill()
turtle.pencolor('white')
for _ in range(300):
turtle.right(1)
turtle.forward(3)
turtle.mainloop()
# ### 反转猜数字，人出数字，计算机猜
# In[1]:
import random
answer = ''
r = random.randint(1,100)
max = 100
min = 1
while answer != '猜对了':
if answer == '偏大':
max = r - 1
r = random.randint(min,max)
elif answer == '偏小':
min = r + 1
r = random.randint(min,max)
print('我猜是',r)
answer = input('')
print('我厉害吧')
# ### 人机猜拳 人机各有1000元，计算机产生随机数，可以下注，谁先输光谁输
# In[17]:
from random import randint
my = ''
m = 0
pd = 0
m_zzc = 1000
c_zzc = 1000
n = 0
while (m_zzc > 0) and (c_zzc > 0):
dz = int(input('请下注，您目前剩余资产为%d 元,电脑剩余资产为%d元，您的下注为'% (m_zzc,c_zzc)))
my = input('猜拳开始')
if my == '石头':
m = 1
elif my == '剪刀':
m = 2
elif my == '布':
m = 3
else:
my = input('输入有误请重新输入')
you = randint(1,3)
if m == 1 and you == 1:
print('平局')
pd = 0
elif m == 1 and you == 2:
print('你赢了')
pd = 1
elif m == 1 and you == 3:
print('电脑胜')
pd = 2
elif m == 2 and you == 1:
print('电脑胜')
pd = 2
elif m == 2 and you == 2:
print('平局')
pd = 0
elif m == 2 and you == 3:
print('你赢了')
pd = 1
elif m == 3 and you == 1:
print('你赢了')
pd = 1
elif m == 3 and you == 2:
print('电脑胜')
pd = 2
elif m == 3 and you == 3:
print('平局')
pd = 0
if pd == 1:
m_zzc +=dz
c_zzc -=dz
elif pd == 2:
m_zzc -=dz
c_zzc +=dz
if m_zzc == 0:
print('您已出局')
else:
print('您赢了电脑')
# ### 个人所得税 总收入 — 五险一金 （输入固定的额）> 3500 税 = （总收入 - 五险一金 - 3500） * 税率 -速算扣除数
# In[5]:
my_salary = float(input('请输入您的工资'))
my_wx = float(input('请输入您要缴纳五险一金的值'))
my_tax = 0
c = 0
if (my_salary - my_wx)<= 3500:
my_tax = 0
else:
c = my_salary - 3500 - my_wx
if c <= 1500:
my_tax = c * 0.03
elif c<= 4500:
my_tax = c * 0.1 - 105
elif c <= 9000:
my_tax = c * 0.2 - 555
elif c <= 35000:
my_tax = c * 0.25 - 1005
elif c <= 55000:
my_tax = c * 0.3 - 2775
elif c <= 80000:
my_tax = c * 0.35 - 5505
else:
my_tax = c * 0.45 - 13505
print('您应缴纳税款%.2f 元，税后工资为%.2f'%(my_tax,my_salary - my_tax - my_wx))