数字和字符串
数字类型
整形
- 整数， 1/2/3/12/2019
- 整形用来描述什么， 身高/年龄/体重
age = 18
height = 180浮点型
浮点数，小数
salary = 10
print(salary)复数
z = 1 + 2j
print(z.real,z.imag)
## 1.0 2.0数字类型方法
print(pow(2,3)) # 幂运算
print(1.2+2.3) # 3.5
print(0.1+0.2) # 0.30000000000000004
print(round(0.1+0.44,1)) # 0.5 四舍五入
print(abs(-1)) # 绝对值
print(divmod(16,3)) # 运算结果(商数， 余数浮点数计算会有误差，小数精准
这就是机器进行二进制计算引入的误差，为了消除这样的误差，进行更加精确的浮点计算，就要是用到decimal模块。
from decimal import *
a = Decimal('0.1') # Decimal函数传入的浮点数必须加引号，构成字符串形式，传入整数就不用了
b = Decimal('0.2')
print(type(a+b),a+b) # 0.3
print(Decimal(0.1)) # 0.1000000000000000055511151231257827021181583404541015625 Decimal函数传入浮点数并不精确
小数的精准计算：
from decimal import *
getcontext().prec = 4 # 设置有效数字为4
print(Decimal('2.2')/Decimal('1.3')) # 1.692from decimal import *
print(Decimal('3.141592653').quantize(Decimal('0.0000'))) # 设定小数位数 这里设置了4位
# 打印结果：3.1416字符串
name = 'neo'
gender = 'male'
print(name, gender)- 三个单引号或三双引号可以换行
poem = '''
When I was a young man, I had liberty, but I did not see it.
I have time, but I did not know it. I have love, but I did not feel it.
Many decades would pass before I understood the meaning of all three.
'''
print(poem)- 引号检测机制
print("neo's name is neo") # 如果字符串中需要有单引号，要用双引号包裹整个字符串
print('''neo's name is "neo"''')- 转义
print('neo\'s name is "neo"') # neo's name is "neo"
print('\tneo') # \t 4个空格，缩进- 换行 \n
print('When I was a young man, I had liberty, but I did not see it.\nI have time, but I did not know it. I have love, but I did not feel it.\nMany decades would pass before I understood the meaning of all three.')
# 打印结果：
When I was a young man, I had liberty, but I did not see it.
I have time, but I did not know it. I have love, but I did not feel it.
Many decades would pass before I understood the meaning of all three.- r 取消转义
print(r'\ta\na')
# 打印结果：\ta\na- \r \r 默认表示将输出的内容返回到第一个指针，这样的话，后面的内容会覆盖前面的内容
字符串运算
print('neo' + '123') # neo123
print('neo'* 4) # neoneoneoneo字符串常用内置方法
s = 'hello world'
res = s.split('o') # 切割
print(res)
# 打印结果：['hell', ' w', 'rld']
print(s.startswith('h')) # 以指定字符串开头,就打印True
print(s.endswith('d'))
print(s.center(20,'*')) # 填充 ****hello world*****- f-string格式化
s1 = 'neo'
s2 = '25'
s3 = 'height'
s4 = 180
print(f'{s1} {s2} {s3} {s4}') # {} 占位，且数字自动转化为字符串
print('{} {} {} {}'.format(s1,s2,s3,s4))- 字符居中/居左/居右
s = 'neo121'
print(f'{s:*^10}') # **neo121**
print(f'{s:*<10}') # neo121****
print(f'{s:*>10}') # ****neo121time模块
import time
print(time.time()) # 从1970.01.01.00:00开始计算时间import time
print('-------')
time.sleep(3) # 睡眠
print('-------')# cpu级别的时间计算，一般用于程序耗时时间计算
import time
start = time.perf_counter()
for i in range(10):
print(i)
time.sleep(0.01)
print(time.perf_counter() - start)
# 打印结果：
0
1
2
3
4
5
6
7
8
9
0.10681829999999998文本进度条
'''
0 %[->..........]
10 %[*->.........]
20 %[**->........]
30 %[***->.......]
40 %[****->......]
50 %[*****->.....]
60 %[******->....]
70 %[*******->...]
80 %[********->..]
90 %[*********->.]
100%[**********->]
'''简单开始
星号在递增，小点在递减，用两个循环
for i in range(10):
print('*'* i + '.' * (10 - i))
# 打印结果：
..........
*.........
**........
***.......
****......
*****.....
******....
*******...
********..
*********.for i in range(10):
print(f'[{"*" * i} -> {"." * (10 - i)}]')
# 打印结果：
[ -> ..........]
[* -> .........]
[** -> ........]
[*** -> .......]
[**** -> ......]
[***** -> .....]
[****** -> ....]
[******* -> ...]
[******** -> ..]
[********* -> .]for i in range(10):
print(f'{i*10: ^3}% [{"*" * i} -> {"." * (10 - i)}]')
# 打印结果：
0 % [ -> ..........]
10 % [* -> .........]
20 % [** -> ........]
30 % [*** -> .......]
40 % [**** -> ......]
50 % [***** -> .....]
60 % [****** -> ....]
70 % [******* -> ...]
80 % [******** -> ..]
90 % [********* -> .]继续修改
scale = 11
for i in range(scale):
print(f'{(i/scale)*scale: ^3.1f}% [{"*" * i} -> {"." * (scale - i)}]')
# 打印结果：
0.0% [ -> ...........]
1.0% [* -> ..........]
2.0% [** -> .........]
3.0% [*** -> ........]
4.0% [**** -> .......]
5.0% [***** -> ......]
6.0% [****** -> .....]
7.0% [******* -> ....]
8.0% [******** -> ...]
9.0% [********* -> ..]
10.0% [********** -> .]单条显示
scale = 101
for i in range(scale):
print(f'\r{(i/scale)*scale: ^3.1f}% [{"*" * i} -> {"." * (scale - i)}]', end='')
# 打印结果：
100.0% [**************************************************************************************************** -> .]文本进度条最终形式
import time
start = time.perf_counter()
scale = 101
for i in range(scale):
print(f'\r{(i / scale) * scale: ^3.1f}% [{"*" * i} -> {"." * (scale - i)}] {time.perf_counter() - start:.2f}s',
end='')
time.sleep(0.1)