print([j for i in [(range(10,100),10),(range(1000,10000),100)] for j in i[0] if (lambda a,b: a == int(str(b)[::-1]))(*divmod(j,i[1]))]) 
 

 
 print([i for i in range(1,2000) if len(str(i))%2 == 0 and str(i) == str(i)[::-1] ]) 
 

There is s that consists of digits from 0 to 9, and an integer k. 
A substring s[L:R] (where 0 = L = R < sizeof(s) ) is a contiguous group of characters with s.  
A substring is called a perfect substring if all of its elements occur exactly k times. 

For example,  s = 1102021222 and k = 2. Its 6 perfect substrings are:

    s[0:1] = 11
    s[0:5] = 110202
    s[1:6] = 102021
    s[2:5] = 0202
    s[7:8] = 22
    s[8:9] = 22

def perfectString(s,k,result):
    for i in range(len(s)):
        num_seen = 0
        window = {}
        for ind in range(i, len(s)):# Range 0 tabanlıdır
            if not s[ind] in window: # ilk kez görüldü
                num_seen += 1  
                window[s[ind]] = 1
            else: # Zaten var
                window[s[ind]] += 1 # arttır
            if   window[s[ind]] == k:
            # 2 ye erişildiyse
                num_seen -= 1
                if num_seen == 0:# Ama window dizisi değişmez
                    result +=1 # Örneğin '211'
                    print(i)
                    print(window)
            elif window[s[ind]] > k:
                print(window)
                break
    return result
print(perfectString("2211",2,0)) # 1102021222