CODEWITHSUNDEEP
pythonpython-3.xstringiterationsequence
Sachihiro
Sachihiro

Reputation: 1783

How to count how many time a sequence appears in a give string in python?

I am trying to count how many time a sequence appears in a given string.

def count_seqence(str, seq):
    count = 0
    if seq in str:
        count += 1
    return count
print(count_seqence("the quick brown fox jumps over the lazy dog","he"))

But this only runs once and does not loop, how can i loop and count how many times appears, because i know looping would be for each char and not a seq, this is making me confusing.

Upvotes: 3

Views: 7328

Answers (4)

ROHAN BOSE
ROHAN BOSE

Reputation: 1

Use count on your string, it will return the number of time it found your parameter value seq

def count_seqence(str, seq): return str.count(seq)

print count_seqence("kjdsflsdnf

Upvotes: 0

willeM_ Van Onsem
willeM_ Van Onsem

Reputation: 476750

Well since you use an if, and not in a loop, that means that either the condition is True, and thus you increment count, or it is False in which case you do not execute the body.

If you want to count numbers, you will need some "looping" mechanism. This does not have to be explicit, for example in hides a loop as well. But this only results in True or False.

Non-overlapping (count_seqence('aaaa', 'aa') is 2)

For non-overlapping counts, we can use str.count:

def count_seqence(text, seq):
    return text.count(seq)

in which case defining a specific function of course is rather useless. Note that the above will only count non-overlapping matches. For example when you count 'aa' in 'aaaa' you will get 2, not 3.

Overlapping (count_seqence('aaaa', 'aa') is 3)

For overlapping, we will need to perform a str.find, and update the "search window" until we no longer find a match, like:

def count_seqence(text, seq):
    cnt = 0
    idx = text.find(seq)
    while idx >= 0:
        cnt += 1
        idx = text.find(seq, idx+1)
    return cnt

We thus have an idx that stores the index where the new match occurs, and each time that idx is larger or equal to 0 (we found a match), we increment cnt, and change idx to the next match.

Upvotes: 6

hearot
hearot

Reputation: 124

Use string.count method. Check Python documentation for that.

Example:

x = "wip wip I'm a sheep wip"
print(x.count("wip"))

Upvotes: 2

Jonathan Gagne
Jonathan Gagne

Reputation: 4379

Use count on your string, it will return the number of time it found your parameter value seq

def count_seqence(str, seq):
    return str.count(seq)

print count_seqence("kjdsflsdnf lskmfldsknffsdlkfnsldkmf", "ds")

Output

2

Upvotes: 4

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