Python | Add leading Zeros to string

Sometimes, during the string manipulation, we are into a problem where we need to pad or add leading zeroes to the string as per the requirements. This problem can occur in web development. Having shorthands to solve this problem turns to be handy in many situations. Let’s discuss certain ways in which this problem can be solved.

Method #1 : Using rjust()

rjust function offers a single line way to perform this particular task. Hence can easily be employed to any string whose padding we need to be done. We can specify the amount of padding required.



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# Python3 code to demonstrate
# adding leading zeros
# using rjust()
  
# initializing string 
test_string = 'GFG'
  
# printing original string 
print("The original string : " + str(test_string))
  
# No. of zeros required
N = 4
  
# using rjust()
# adding leading zero
res = test_string.rjust(N + len(test_string), '0')
  
# print result
print("The string after adding leading zeros : " + str(res))

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Output :

The original string : GFG
The string after adding leading zeros : 0000GFG

 

Method #2 : Using zfill()

This is yet another way to perform this particular task, in this function we don’t need to specify the letter that we need to pad, this function is exclusively made to pad zeros internally and hence recommended.

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# Python3 code to demonstrate
# adding leading zeros
# using zfill()
  
# initializing string 
test_string = 'GFG'
  
# printing original string 
print("The original string : " + str(test_string))
  
# No. of zeros required
N = 4
  
# using zfill()
# adding leading zero
res = test_string.zfill(N + len(test_string))
  
# print result
print("The string after adding leading zeros : " + str(res))

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Output :

The original string : GFG
The string after adding leading zeros : 0000GFG


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