Python | Check Numeric Suffix in String

Sometimes, while programming, we can have such a problem in which we need to check if any string is ending with a number i.e it has a numeric suffix. This problem can occur in Web Development domain. Let's discuss certain ways in which this problem can be solved. 

Method #1: Using regex 
This problem can be solved using regex. The search and group function can perform the task of searching the suffix string and printing the number, if it is required. 

# Python3 code to demonstrate working of 
# Check Numeric Suffix in String 
# Using regex 
import re 

# initializing string 
test_str = "Geeks4321"

# printing original string 
print("The original string is : " + str(test_str)) 

# Using regex 
# Check Numeric Suffix in String 
res = re.search(r'\d+$', test_str) 

# printing result 
print("Does string contain suffix number ? : " + str(bool(res))) 

The original string is : Geeks4321
Does string contain suffix number ? : True

Method #2: Using isdigit() 

The isdigit function can be used to perform this particular task using the fact that if a number at the end, means its very last character is going to be a number, so by just checking the last character, we can prove that a string ends with a number. 

# Python3 code to demonstrate working of 
# Check Numeric Suffix in String 
# Using isdigit() 

# initializing string 
test_str = "Geeks4321"

# printing original string 
print("The original string is : " + str(test_str)) 

# Using isdigit() 
# Check Numeric Suffix in String 
res = test_str[-1].isdigit() 

# printing result 
print("Does string contain suffix number ? : " + str(res)) 

The original string is : Geeks4321
Does string contain suffix number ? : True

The time complexity of this program is O(1) since it only checks if the last character of the input string is a digit using the isdigit() method. 

The auxiliary space required is also O(1) since the program does not use any additional data structures and only stores the result of the isdigit() method in a boolean variable res.

Method #3: Without using inbuilt function

# Python3 code to demonstrate working of
# Check Numeric Suffix in String

# initializing string
test_str = "Geeks4321"

# printing original string
print("The original string is : " + str(test_str))

res = False
numbers = "0123456789"
if test_str[-1] in numbers:
    res = True
# printing result
print("Does string contain suffix number ? : " + str(res))

The original string is : Geeks4321
Does string contain suffix number ? : True

Time Complexity: O(1)
Auxiliary Space: O(1)

Method 4: Using the try and except block

This method using try and except block, try to convert the last character of string to int. If it throws error i.e. not a number, returns False, otherwise returns true.

# Python3 code to demonstrate working of
# Check Numeric Suffix in String
# Using try-except block

# initializing string
test_str = "Geeks4321"

# printing original string
print("The original string is : " + test_str)

res = False

try:
    int(test_str[-1])
    res = True
except ValueError:
    res = False

# printing result
print("Does string contain suffix number ? : " + str(res))

#This code is contributed by Edula Vinay Kumar Reddy

The original string is : Geeks4321
Does string contain suffix number ? : True

Time complexity: O(1)
Auxiliary Space: O(1)

Method 5: Using str.isdecimal() method

# Python3 code to demonstrate working of
# Check Numeric Suffix in String

# initializing string
test_str = "Geeks4321"

# printing original string
print("The original string is : " + str(test_str))

res = False
if test_str[-1].isdecimal():
    res = True
# printing result
print("Does string contain suffix number ? : " + str(res))
#This code is contributed by Vinay Pinjala.

The original string is : Geeks4321
Does string contain suffix number ? : True

Time complexity: O(1)
Auxiliary Space: O(1)

Method 6: Using reduce():

Step-by-step approach:

• Import the reduce() function from the functools module.
• Initialize the string to be tested.
• Use the reduce() function to iterate through the characters of the string from the end and check if the last character is a number.
• If the last character is numeric, the lambda function returns True and the next character is checked.
• If all characters are numeric, the final value returned by reduce() is True.
• Print the result.

from functools import reduce

test_str = "Geeks4321"
# printing original string
print("The original string is : " + str(test_str))
# using reduce to check if last character is numeric
res = reduce(lambda x, y: y.isnumeric(), test_str[-1], False)

print("Does string contain suffix number? : " + str(res))
#This code is contributed by Pushpa.

The original string is : Geeks4321
Does string contain suffix number? : True

Time Complexity:
The time complexity of the reduce() function is O(n), where n is the length of the input string. Since the lambda function is called once for each character in the string, the overall time complexity of the algorithm is also O(n).

Space Complexity:
The space complexity of the algorithm is O(1), since only a few variables are used to store the input string and the result, and their space requirements do not depend on the length of the string. The lambda function used in the reduce() function does not create any additional data structures that would increase the space complexity. Therefore, the overall space complexity of the algorithm is constant.

Method #7: Using a loop to iterate over the characters

• Initialize the string to be checked for a numeric suffix.
• Initialize a boolean variable res to False.
• Use a loop to iterate over the characters in the string from right to left.
• For each character, check if it is a digit using the isdigit() method.
• If the character is a digit, set res to True and break out of the loop.
• If the character is not a digit, set res to False and continue iterating over the rest of the string.
• Print the result.

# initializing string
test_str = "Geeks4321"

# printing original string
print("The original string is : " + test_str)

res = False

# use a loop to iterate over the characters in the string
for c in reversed(test_str):
    # check if the character is a digit
    if c.isdigit():
        res = True
        break
    else:
        res = False

# printing result
print("Does string contain suffix number? : " + str(res))

The original string is : Geeks4321
Does string contain suffix number? : True

Time complexity: O(n), where n is the length of the string.
Auxiliary space: O(1), as the space used is constant regardless of the input size.

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