Question

May be a little too many for today.. but meh.

This problem is pretty confusing to me. This function takes a list of strings as a parameter and returns every string that is a substring of the one that precedes it. So

1. [“hope”, “hop”, “hopefully”, “test”, “testing”] will return [‘hop’]
2. [“hopefully”, “hope”, “hop”, “testing”, “test”] will return [‘hope’, ‘hop’, ‘test’]

Excuse the mess of code here, I’m still learning.

def findSubStrs(lst):
'list ==> list, return list of all strings that are substrings of their predecessor in lst'
res = []
for a in lst:
    if len(int(a-1)) > len(lst):
        res = res + [a]
return res

I figured that len(int(a-1)) would work to check the preceding string, but I just got the error message “TypeError: unsupported operand type(s) for -: ‘str’ and ‘int'” The only result I found that worked was len(a) < 3 or some other int, but that doesn’t return everything I need.

Answer 1

how bout

print [my_list[i] for i in range(1,len(my_list)) if my_list[i] in my_list[i-1]]

for example

>>> def findSubStrs(my_list):
...     return [my_list[i] for i in range(1,len(my_list)) if my_list[i] in my_list[i-1]]
>>> findSubStrs(["hope", "hop", "hopefully", "test", "testing"] )
['hop']
>>> findSubStrs(["hopefully", "hope", "hop", "testing", "test"])
['hope', 'hop', 'test']

to do this without a list comprehension you can just use a simple loop

for i in range(1,len(my_list)):
    if my_list[i] in my_list[i-1]:
        print my_list[i]