Python | Ways to count number of substring in string

Given a string and a substring, write a Python program to find how many numbers of substring are there in the string (including overlapping cases). Let’s discuss a few methods below.

Method #1: Using re.findall()

# Python code to demonstrate  
# to count total number 
# of substring in string 
  
import re 
# Initialising string 
ini_str = "ababababa"
sub_str = 'aba'
  
# Count count of substrings using re.findall 
res = len(re.findall('(?= aba)', ini_str)) 
  
# Printing result 
print("Number of substrings", res) 

Output:

Number of substrings 0

Method #2: Using re.finditer()

# Python code to demonstrate  
# to count total number 
# of substring in string 
  
import re 
# Initialising string 
ini_str = "ababababa"
sub_str = 'aba'
  
# Count count of substrings using re.finditer 
res = sum(1 for _ in re.finditer('(?= aba)', ini_str)) 
  
# Printing result 
print("Number of substrings", res) 

Output:

Number of substrings 0

Method #3: Using startswith()

# Python code to demonstrate  
# to count total number 
# of substring in string 
  
# Initialising string 
ini_str = "ababababa"
sub_str = 'aba'
  
# Count count of substrings using startswith 
res = sum(1 for i in range(len(ini_str))  
         if ini_str.startswith("aba", i)) 
  
# Printing result 
print("Number of substrings", res) 

Output:

Number of substrings 4

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