dataString = "Substring removing"

dataString = dataString[:9]
# dataString is "Substring"
print(dataString)

dataString = dataString[3:]
# dataString is "string"
print(dataString)

# *** in version 3.9: ***
dataString = "Substring removing"

dataString = dataString.removesuffix(' removing')
# dataString is "Substring"
print(dataString)

dataString = dataString.removeprefix('Sub')
# dataString is "string"
print(dataString)