Need "sum" compatible checksum16 in Python

[Costas Menico]

He is the equivalent in Python.

def calcChecksum(aString):
    checksum = 0
    for aChar in aString:
        aChar = ord(aChar)
        if aChar & 01:  aChar = (aChar >>1) + 0x8000  
        else: aChar >>= 1
        checksum += aChar 
        checksum &= 0xffff
    return checksum


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