python怎么判断是否为字符

A = 123

B = [123.'A']

C = {'A':123,'B':45}

D = 1.23

E = 'abc'

isinstance(A, int)    #True

isinstance(B, list)   #True

isinstance(C, dict)   #True

isinstance(D, float)  #True

isinstance(E, str)    #True

type(A)== type(1)     #True

type(B)== type([])    #True