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Python | Check whether string contains only numbers or not

  • Difficulty Level : Basic
  • Last Updated : 22 Sep, 2021

Given a string, write a Python program to find whether a string contains only numbers or not. Let’s see a few methods to solve the above task.
Method #1: Using isdigit() method 
 

Python3




# Python3 code to demonstrate
# how to check whether string contains
# only numbers or not
 
# Initialising string
ini_string1 = '1234556'
ini_string2 = 'ab123bc'
 
# printing initial string
print ("Initial Strings : ", ini_string1, ini_string2)
 
# Using isdigit()
if ini_string1.isdigit():
    print ("String1 contains all numbers")
else:
    print ("String1 doesn't contains all numbers")
     
if ini_string2.isdigit():
    print ("String2 contains all numbers")
else:
    print ("String2 doesn't contains all numbers")
Output: 
Initial Strings :  1234556 ab123bc
String1 contains all numbers
String2 doesn't contains all numbers

 

  
Method #2: Using regex 
 

Python3




# Python3 code to demonstrate
# how to check whether string contains
# only numbers or not
import re
 
# Initialising string
ini_string1 = '1234556'
ini_string2 = 'ab123bc'
 
# printing initial string
print ("Initial Strings : ", ini_string1, ini_string2)
 
# Using regex()
if re.match('^[0-9]*$', ini_string1):
    print ("String1 contains all numbers")
else:
    print ("String1 doesn't contains all numbers")
     
if re.match('^[0-9]*$', ini_string2):
    print ("String2 contains all numbers")
else:
    print ("String2 doesn't contains all numbers")
Output: 
Initial Strings :  1234556 ab123bc
String1 contains all numbers
String2 doesn't contains all numbers

 

  
Method #3: Using try/exception 
 

Python3




# Python3 code to demonstrate
# how to check whether string contains
# only numbers or not
 
# Initialising string
ini_string1 = '1234556'
ini_string2 = 'abc123'
 
# printing initial string
print ("Initial Strings : ", ini_string1, ini_string2)
 
# Using try / exception:
try:
    num = int(ini_string1)
    print ("String1 contains only digits")
except:
    print ("String1 doesn'tcontains only digits")
     
try:
    num = int(ini_string2)
    print ("String2 contains only digits")
except:
    print ("String2 doesn't contains only digits")
    
Output: 
Initial Strings :  1234556 abc123
String1 contains only digits
String2 doesn't contains only digits

 


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