How to count the number of substrings in a string? - python-3.x

I want to find the number of occurrences of a particular sub-string in a string.
string="abcbcbcb"
sub_str="cbc"
c=string.count(sub_str)
print(c)
This gives the output as
1
which is the number of non-overlapping occurrences of substring in the string.
But I want to calculate the overlapping strings as well. Thus, the desired output is:
2

You can use a regular expression, use module "re"
print len(re.findall('(?=cbc)','abcbcbcb'))

No standard function available for overlapping count. You could write custom function tho.
def count_occ(string, substr):
cnt = 0
pos = 0
while(True):
pos = string.find(substr , pos)
if pos > -1:
cnt += 1
pos += 1
else:
break
return cnt
string="abcbcbcb"
sub_str="cbc"
print(count_occ(string,sub_str))

Related

Recursive function how to manage output

I'm working on a project for creating some word list. I have a word and some rules, for example, this char % is for digit, while this one ^ for special character, for example January%%^ should create things like:
January00!
January01!
January02!
January03!
January04!
January05!
January06!
etc.
For now I'm trying to do it with only digit and create a recursive function, because people can add as many digits and special characters as they want
January^%%%^% (for example)
This is the first function I have created:
month = "January"
nbDigit = "%%%"
def addNumber(month : list, position: int):
for i in range(position, len(month)):
for j in range(0,10):
month[position] = j
if(position == len(month)-1):
print (''.join(str(v) for v in month))
if position < len(month):
if month[position+1] == "%":
addNumber(month, position+1)
The problem is for each % that I have there is another output (three %, three times as output January000-January999/January000-January999/January000-January999).
When I tried to add the new function special character it's even worse, because I can't manage the output since every word can't end with a special character or digit. (AddSpecialChar is also a recursive function).
I believe what you are looking for is the following:
month = 'January'
nbDigit = "%%"
def addNumbers(root: str, mask: str)-> list:
# create a list of words using root followed By digits
rslt = []
mxNmb = 0
for i in range(len(mask)):
mxNmb += 9 * 10**i
mxNmb += 1
for i in range(mxNmb):
word = f"{root}{((str(i).rjust(len(mask), '0')))}"
rslt.append(word)
return rslt
this will produce:
['January00',
'January01',
'January02',
'January03',
'January04',
'January05',
'January06',
'January07',
'January08',
'January09',
'January10',
'January11',
'January12',
'January13',
'January14',
'January15',
'January16',
'January17',
'January18',
'January19',
'January20',
'January21',
'January22',
'January23',
'January24',
'January25',
'January26',
'January27',
'January28',
'January29',
'January30',
'January31',
'January32',
'January33',
'January34',
'January35',
'January36',
'January37',
'January38',
'January39',
'January40',
'January41',
'January42',
'January43',
'January44',
'January45',
'January46',
'January47',
'January48',
'January49',
'January50',
'January51',
'January52',
'January53',
'January54',
'January55',
'January56',
'January57',
'January58',
'January59',
'January60',
'January61',
'January62',
'January63',
'January64',
'January65',
'January66',
'January67',
'January68',
'January69',
'January70',
'January71',
'January72',
'January73',
'January74',
'January75',
'January76',
'January77',
'January78',
'January79',
'January80',
'January81',
'January82',
'January83',
'January84',
'January85',
'January86',
'January87',
'January88',
'January89',
'January90',
'January91',
'January92',
'January93',
'January94',
'January95',
'January96',
'January97',
'January98',
'January99']
Adding another position to the nbDigit variable will produce the numeric sequence from 000 to 999

Problem with Python Code and the Functions in it

I have a Problem, I have to solve a task in Python and I dont know how to do it. The task is to define a function number_of_vowels, where the output should be the Number of vowels in a Word. With this function I have to write anotherone, many_vowels thats working with a list an a Number and where the number says how many vowels have to be at least in a word to be appended to the result list and then I have to append this Word. Thanks to everybody helping me ;D.
here is the code:
Wort = "parameter"
def number_of_vowels(Word):
result = 0
counter0 = 0
while result < 20:
if Word[counter0] == 'a' or 'e' or 'i' or 'o' or 'u':
result = result + 1
counter0 = counter0 + 1
else:
counter0 = counter0 + 1
return result
Words = []
counter1 = 0
def many_vowels(List , number):
if number_of_vowels(List[counter1]) < number:
counter1 + 1
else:
Words.append(List[counter1])
counter1 + 1
return Words
This code just gives me the answer to the letter a and not to the other vowels. For
print(number_of_vowels(Wort))
the output is: 1
but there are 4 vowels in this word
it also says: line 21, in many_vowels
IndexError: string index out of range
You're trying to call a function with wrong brackets. Function call should use round ones.
Try changing number_of_vowels[List[counter1]] with number_of_vowels(List[counter1])
This code contains some errors:
Calling for function should be using round brackets: number_of_vowels(List[counter1]) instead of number_of_vowels[List[counter1]]
doing result + 1 won't change value of the variable result, since you did not put the calculation result in the variable. use result = result + 1 (same for counters)
in number_of_vowels function, you want to scan the whole word? cause you did not use any loop, so it currently looking only at the first letter. Secondly, you put the compression in result and then add 1 to it. I'm not really sure why
edit:
Word = "parameter"
def number_of_vowels(Word):
result = 0
counter0 = 0
for index, letter in enumerate(Word):
if letter == 'a' or letter == 'e' or letter == 'i' or letter == 'o' or letter == 'u':
result = result + 1
return result
Words = []
counter1 = 0
def many_vowels(List_name , number):
for index, item in enumerate (List_name):
if number_of_vowels(item) >= number:
Words.append(item)
return Words

Palindrome rearrangement in Python

I am given a string and I have to determine whether it can be rearranged into a palindrome.
For example: "aabb" is true.
We can rearrange "aabb" to make "abba", which is a palindrome.
I have come up with the code below but it fails in some cases. Where is the problem and how to fix this?
def palindromeRearranging(inputString):
a = sorted(inputString)[::2]
b = sorted(inputString)[1::2]
return b == a[:len(b)]
def palindromeRearranging(inputString):
return sum(map(lambda x: inputString.count(x) % 2, set(inputString))) <= 1
this code counts occurrence for every character in string. in palindromes there is one character with odd occurrence if length of string is odd, if length of string is even then no character has odd occurance.
see here
def palindromeRearranging(inputString):
elements = {c:inputString.count(c) for c in set(inputString)}
even = [e % 2 == 0 for e in elements.values()]
return all(even) or (len(inputString) % 2 == 1 and even.count(False) == 1)
It counts each character number of appearances, and checks whether all elements appear an even number of times or if the length of the input string is odd, checks whether only one character appears an odd number of times.
Python3
def palindromeArrange (string):
string = list(string)
for i in range (len(string)):
"""if the string has even element count"""
if len(string) % 2 == 0 and len(string)/2 == len (set (string)):
return True
"""if the string has odd element count"""
if len(string) - ((len(string)-1)/2) == len (set (string)):
return True
return False
One liner using list comprehension in Python3
return len([x for x in set(inputString) if inputString.count(x) % 2 != 0]) <= 1
Basically counts those characters that have counts that aren't divisible by 2.
For even strings it would be zero, and for odd strings, it would be one.
The solution I can think of right away has time complexity is O(n). The assumption is, palindrome can not be made if there is more than one character with the odd count.
def solution(inputString):
string = list(inputString)
n = len(string)
s_set= set(string)
from collections import Counter
dic = Counter(string)
k =0 #counter for odd characters
for char in s_set:
if dic.get(char)%2!=0:
k+=1
if k>1:
return False
else:
return True

Strings in python 3.7

How to count sub-strings in a string?
Example: findSubstrings("foxcatfox","fox") # should return 2
If recursion is really a must, you can try dividing the problem first.
Say if you found a matching substring at position i, then the total number of substring is 1 + findSub(string[i+1:], sub), so you can write something like this:
def findSubstringsRecursive(string, substring):
counter = 0
substringLength = len(substring)
for i in range(len(string)):
if string[i] == substring[0]:
end = i + substringLength
sub1 = string[i:end]
if substring == sub1:
return 1 + findSubstringsRecursive(string[i+1:], substring)
return 0
The following pure recursive approach is simple enough (apart from the bool->int coercion):
def findRec(s, pat):
if len(s) < len(pat): # base case should be obvious
return 0
return (pat == s[:len(pat)]) + findRec(s[1:], pat) # recurse with smaller size
>>> findSubstrings('foxcatfox', 'fox')
2
>>> findSubstrings('foxcatfox', 'foxc')
1
>>> findSubstrings('foxcat', 'dog')
0
I should note that this counts overlapping occurrences which may or may not be desired. One might also add protection against or define behaviour for an empty substring.

Return number of alphabetical substrings within input string

I'm trying to generate code to return the number of substrings within an input that are in sequential alphabetical order.
i.e. Input: 'abccbaabccba'
Output: 2
alphabet = 'abcdefghijklmnopqrstuvwxyz'
def cake(x):
for i in range(len(x)):
for j in range (len(x)+1):
s = x[i:j+1]
l = 0
if s in alphabet:
l += 1
return l
print (cake('abccbaabccba'))
So far my code will only return 1. Based on tests I've done on it, it seems it just returns a 1 if there are letters in the input. Does anyone see where I'm going wrong?
You are getting the output 1 every time because your code resets the count to l = 0 on every pass through the loop.
If you fix this, you will get the answer 96, because you are including a lot of redundant checks on empty strings ('' in alphabet returns True).
If you fix that, you will get 17, because your test string contains substrings of length 1 and 2, as well as 3+, that are also substrings of the alphabet. So, your code needs to take into account the minimum substring length you would like to consider—which I assume is 3:
alphabet = 'abcdefghijklmnopqrstuvwxyz'
def cake(x, minLength=3):
l = 0
for i in range(len(x)):
for j in range(i+minLength, len(x)): # carefully specify both the start and end values of the loop that determines where your substring will end
s = x[i:j]
if s in alphabet:
print(repr(s))
l += 1
return l
print (cake('abccbaabccba'))

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