The use of the Python eval () function

The use of the Python eval () function

The eval (str) function is powerful, as the official explanation is that the string STR is evaluated as a valid expression and returns the result of the calculation. So it's good to combine math as a calculator.

The most common functions of the eval () function are:
1. Evaluates a valid expression in a string and returns the result

1 >>> eval ('pow (2,2)')2 43 >>> Eval ('2 + 2')4 45 >>> eval ("n + 4")6 85

2. Convert the string to the corresponding object (such as the conversion between list, tuple, dict, and string)

1>>> A ="[ [up], [3,4], [5,6], [7,8], [9,0]]"2>>> B =Eval (a)3>>>b4[[1, 2], [3, 4], [5, 6], [7, 8], [9, 0]]5>>> A ="{1: ' xx ', 2: ' yy '}"6>>> C =Eval (a)7>>>C8{1:'xx', 2:'yy'}9>>> A ="(1,2,3,4)"Ten>>> d =Eval (a) One>>>D A(1, 2, 3, 4)

3. Convert the string back to the object using the anti-quote conversion

1>>> List1 = [1,2,3,4,5]2>>>' List1 '3 '[1, 2, 3, 4, 5]'4>>>type (' List1 ')5<type'Str'>6>>>Type (eval (' List1 '))7<type'List'>8>>> A =eval (' List1 ')9>>>aTen[1, 2, 3, 4, 5]

The use of the Python eval () function