The slice ( : ) operator in Python allows you to obtain a part of string. The slice operator has two operands, index of beginning of slice and end of slice.
substr = var[x:y]
In following example, three characters from 7th characters are obtained ( Python sequence uses zero based index)
>>> var="Hello how are you?" >>> str1=var[6:9] >>> str1 'how'
In order to obtain first 100 characters,
>>> str1=var[0:100]