Program to find whether a string is substring of another string

Question

str1 is a string in which the search is to be performed (the haystack). str2 is the string to be found (the needle). count will count the number of occurences of str2 in str1.

The code below gives me a syntax error in the last line. Please suggest changes.

str1 = raw_input()
str2 = raw_input()
count = 0
for i in range(0,len(str1)) :

    if ( str1.find(str2, i, i+len(str2))) : 
        count=count+1
print count

@PadraicCunningham I don't get it.. what do you mean by overlapping strings? — Maroun, Jan 22 '15 at 12:42
@MarounMaroun, the OP seems to be counting so they seem to want to find all occurrences so "bobob".count("bob") = 1 when it is 2 if you consider overlapping strings — Padraic Cunningham, Jan 22 '15 at 12:44

score 4 · Answer 1 · answered Jan 22 '15 at 12:40

4

To find out if a string is a substring of another string, you can use the in operator

"abc" in "abcd" # will return true

And to count occurences you can use the count method of string

"abcda".count("a") # will return 2

answered Jan 22 '15 at 12:40

Dave

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Padraic Cunningham · Answer 2 · 2015-01-22T12:56:12.837

3

If you want to count how many times str2 is in str1 including overlapping strings:

str1 = raw_input() # input() if using python3
str2 = raw_input() 
print(sum(str1[i:i+len(str2)] == str2 for i in xrange(len(str1)) ))

Example:

In [12]: paste
str1 = raw_input()
str2 = raw_input()
sum(str1[i:i+len(str2)] == str2 for i in xrange(len(str1)))

## -- End pasted text --
bobob
bob
Out[12]: 2

edited Jan 22 '15 at 12:56

answered Jan 22 '15 at 12:42

Padraic Cunningham

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good answer, this covers overlapping strings too. – Maroun Jan 22 '15 at 12:44
1

@MarounMaroun, i may be wrong but the OP's code does look like some attempt at doing the same. – Padraic Cunningham Jan 22 '15 at 12:45

Program to find whether a string is substring of another string

2 Answers2