Why does lambda throw 'name value_o is not defined' error?

[Axel_Erfurt]

def decrypt(text,n):
    value_e = []
    value_o = []
    i=0
    test=""
    if n<0:
        text=text
    else:
        while i<n:
            for index,value in enumerate(text):
                value_e=[value for index, value in enumerate(text) if index<len(text)/2]
                value_o=[value for index, value in enumerate(text) if index>=len(text)/2]
            i+=1
    print(value_e)
    print(value_o)
    for x in map(lambda x,y : x+y, value_o, value_e):
        test+= x

decrypt("hello world", 11)

Output:
['h', 'e', 'l', 'l', 'o', ' ']
['w', 'o', 'r', 'l', 'd']