运算符

算数运算

如a=10,b=20

+两个数相加 a+b=30

-两个数相减 a-b=-10

两个数相乘 a****b =200

/两个数相除b/a=2

%取模，并返回余数b%a=0

幂，a****b**=10的20次方

.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"33[1;31mr[{a}->{b}]{c:.2f}%{res:.2f}s33[0m",end="")
  # 上面加了就可以改变颜色
  #print(f"33[1;31;40mr[{a}->{b}]{c:.2f}%{res:.2f}s33[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,‘-‘))

  ```