5 replies to this topic

[Lucifer_Alpha]

Please, could someone help with this code. I want to write a function which takes a string and check how many times some other string appears in it.

Below is my totally incompetent attempt. I have written like only 3 codes -- ever. If someone could explain what is wrong with python that it gives me an error, that would be helpful.

from string import *


def countMatches(target,key):

    l = []

    def checkandmakelist(target,key): 

        if find(target,key) != -1:

            global l

            l = l + [str(find(target,key))]

            target = target[find(target,key):]

            checkandmakelist(target,key)

            print len(l)

        else:

            print "not there"

    checkandmakelist(target,key)

    

countMatches("sfsddfzwefdffe","df")

python 2.7 btw

[Sysop_fb]

Is there a reason you can't use the standard string count method?

>>> s = "hello there hello how are you hello"
>>> s.count("hello")
3
>>> "hello there hello how are you hello".count("hello")
3
>>> "hello there hello how are you hello".count("hellow")
0
>>> 

[Lucifer_Alpha]

That is not allowed.

My problem set says: "Write two functions, calledcountSubStringMatch and countSubStringMatchRecursive that take two arguments, a key string and a target string. These functions iteratively and recursively count the number of instances of the key in the target string." I have not learned count and it is not in any of the readings. So, it's safe to assume I can't use it.

This is for the ocw intro to cs course, btw.

---------- Post added at 12:14 PM ---------- Previous post was at 12:00 PM ----------

How do I view the source code for your count function? That would help.
Oh, is there a source code encyclopedia or something somewhere?

[Sysop_fb]

They taught you how to do subscripting and for loops right? So if I wanted to print out every 5 subsequent letters from the string
"hellotherehitherehello"

string = "hellotherehitherehello"
key = "hello"
for i in range(0,len(string)-1):
     print string[i:i+len(key)]

Unsure if that code will work in 3 though because it goes out of bounds but you can fix that pretty easily if you think about it.

[JackomoLight]

Sysop_fb, on 03 February 2012 - 05:25 PM, said:

Is there a reason you can't use the standard string count method?

>>> s = "hello there hello how are you hello"
>>> s.count("hello")
3
>>> "hello there hello how are you hello".count("hello")
3
>>> "hello there hello how are you hello".count("hellow")
0
>>>

Is there a way to get the indices of all of the occurrences of the string?

[Flying Dutchman]

You can with regular expressions or with find method. find returns the index of the match and you can also specify offset.