Question

I’m following a python website for my schoolwork. It’s really neat, it gives you tasks to complete and compiles the code in the browser. Anyway, I came to a challenge that I’m not really sure how to go about.

One of the questions was:

The same substring may occur several times inside the same string: for example “assesses” has the substring “sses” 2 times, and
“trans-Panamanian banana” has the substring “an” 6 times. Write a
program that takes two lines of input, we call the first needle and
the second haystack. Print the number of times that needle occurs as a
substring of haystack.

I’m not too sure how I should start this, I know I have to compare the two strings but how? I used the count method, but it didn’t recognize the second occurrence of sses in assesses.

My second question is one I solved but I cheated a little.

The question was:

Write a program that takes a single input line of the form «number1»+«number2», where both of these represent positive integers,
and outputs the sum of the two numbers. For example on input 5+12 the
output should be 17.

I used the eval() method and it worked, I just think that this wasn’t what the grader had in mind for this.

Any insight would be greatly appreciated.

EDIT: Second question was solved.

Answer 1

For the first question, str.count() does not find overlapping matches, as you noticed. Instead, use str.find() and advance your starting index after each time you find a match, until the result is -1, for example:

>>> 'assesses'.find('sses', 0)    # first look at the start of the string
1
>>> 'assesses'.find('sses', 2)    # now look at previous index + 1
4
>>> 'assesses'.find('sses', 5)    # now look at previous index + 1
-1

Since there were two results before we got -1, we know that there are two locations to find 'sses' in 'assesses'.

For you second question, you will need to split() the string on '+', which will give you a list of two strings. Call int() on each of them, and then add them together.