eval()函数将公式字符串转换成公式

a = eval("1+2")print(a,type(a))  # 3 
     
      b = eval("True")print(b,type(b))  # True 
      
       c = eval("1==2")print(c,type(c))  # False 
       
        d = eval("true")print(d)  # NameError: name 'true' is not defined
       
      
     

eval()函数实现list、dict、tuple与str之间的转化

• 字符串转换成列表

a = "[1,2,3]"print(a,type(a))  # [1,2,3] 
     
      b = eval(a)print(b,type(b))  # [1, 2, 3] 
      
     

• 字符串转换成元组

a = "(1,2,3)"print(a,type(a))  # (1,2,3) 
     
      b = eval(a)print(b,type(b))  # (1, 2, 3) 
      
     

• 字符串转换成字典

a = "{1:'a',2:2,3:[1,2,3]}"print(a,type(a))  # {1:'a',2:2,3:[1,2,3]} 
     
      b = eval(a)print(b,type(b))  # {1: 'a', 2: 2, 3: [1, 2, 3]}