# 运算符

### 算数运算

+两个数相加 a+b=30

-两个数相减 a-b=-10

/两个数相除b/a=2

%取模，并返回余数b%a=0

.strip()去除多余空格字符串

.isdigit()判断是否为数字字符串

## time库

• 获取时间

time.timr()

time.ctime()

time.gmtime()

• 格式化

? time.strftime

? time.strptime

• 程序计时

time.sleep()

time.perf_counter()

### 利用time库写一个进度条

• 源代码

```import time

count = 10
print("....请开始执行....")
for i in range(count + 1):
a = "#" * i
b = "." * (count - i)
c = (i/count) * 100
print(f"[{a}->{b}]{c}%")
time.sleep(0.2)
print("......执行结束.....")```

### 优化后的进度条

• 源代码

```python
import time

print("开始执行".center(50, ‘-‘))#把开始执行放中间，用50个-包围
start = time.perf_counter()
count = 100
for i in range(count + 1):
a = "#" * i
b = "." * (count - i)
c = (i/count) * 100
res = time.perf_counter() - start
#print(f"\r[{a}->{b}]{c:.2f}%{res:.2f}s",end="")
print(f"\033[1;31m\r[{a}->{b}]{c:.2f}%{res:.2f}s\033[0m", end="")
# 上面加了就可以改变颜色
#print(f"\033[1;31;40m\r[{a}->{b}]{c:.2f}%{res:.2f}s\033[0m", end="")
#上面这行还可以改变进度条背景颜色
time.sleep(0.05)
print("\n" + "结束执行".center(50, ‘-‘))

```