Remove leading zeros from a Number given as a string using Python

In this article, we will learn a python program to remove leading zeros from a number given as a string.

Assume we have taken a number in string format. We will now remove all the leading zeros(zeros present at the beginning of a number) using the below-given methods.

Methods Used

The following are the various methods used to accomplish this task −

• Using For Loop and remove() function

• Using Regex

• Using int() Function

Method 1: Using For Loop and remove() function

Algorithm (Steps)

Following are the Algorithms/steps to be followed to perform the desired task. −

• Create a function deleteLeadingZeros() that removes the leading zeros from a number passed as a string to the function.

• Use the for loop, to traverse through the length of the string using the len() function.

• len() function − The number of items in an object is returned by the len() method. The len() function returns the number of characters in a string when the object is a string.

• Use the if conditional statement along with != operator to check whether the current character in a string is not 0

• Get the remaining characters of the string after the leading zeros using slicing.

• Return the resultant string after removing all the leading 0s from the input string.

• Return 0 if there are no leading 0s found.

• Create a variable to store the input number passed as a string.

• Call the above-defined deleteLeadingZeros() function by passing the input string to it to get the resultant string after removing leading zeros.

• In the same way check for the other string having no leading zeros.

Example

The following program returns as a string that removes all the leading zeros from a number passed as a string using for Loop and remove() function −

# creating a function that removes the leading zeros
# from a number passed as a string to the function
def deleteLeadingZeros(inputString):
   # traversing through the length of the string
   for k in range(len(inputString)):
      # checking whether the current character of a string is not 0
      if inputString[k] != '0':
         # getting the remaining string using slicing
         outputString= inputString[k::]
         # returning resultant string after removing leading 0s
         return outputString
   # returning 0 if there are no leading 0s found in the entire string
   return "0"
# input number as a string
inputString = "0002056"
print("Given String is:", inputString)
# calling the deleteLeadingZeros() function by passing the input string to it
print("After Removing Leading Zeros:", deleteLeadingZeros(inputString))
# checking it for other strings having no leading 0s
inputString = "256"
print("Given String is:", inputString)
# calling the deleteLeadingZeros() function by passing the input string to it
print("After Removing Leading Zeros:", deleteLeadingZeros(inputString))

Output

On execution, the above program will generate the following output −

Given String is: 0002056
After Removing Leading Zeros: 2056
Given String is: 256
After Removing Leading Zeros: 256

Method 2: Using Regex

Algorithm (Steps)

Following are the Algorithms/steps to be followed to perform the desired task. −

• Use the import keyword to import the regex(re) module.

• Create a function deleteLeadingZeros() that removes the leading zeros from a number passed as a string to the function.

• Create a variable to store the regex pattern for removing leading zeros from an input string.

• Replace the matched regex pattern with an empty string using the sub() function.

• sub() function(returns a string in which all the matching occurrences of the given pattern are replaced by the replace string).

• Print the resultant string after removing all the leading 0s from the input string.

Example

The following program returns as a string that removes all the leading zeros from a number passed as a string using regular expressions −

# importing re module
import re
# creating a function that removes the leading zeros
# from a number passed as a string to the function
def deleteLeadingZeros(inputString):
   # regex pattern for removing leading zeros from an input string
   regexPattern = "^0+(?!$)"
   # Replace the matched regex pattern with an empty string
   outputString = re.sub(regexPattern, "", inputString)
   # returning output string after removing leading 0s
   return outputString
# input number as a string
inputString = "0002056"
print("Given String is:", inputString)
# calling the deleteLeadingZeros() function by passing the input string to it
print("After Removing Leading Zeros:", deleteLeadingZeros(inputString))

Output

On execution, the above program will generate the following output −

Given String is: 0002056
After Removing Leading Zeros: 2056

Method 3: Using int() Function

Algorithm (Steps)

Following are the Algorithms/steps to be followed to perform the desired task. −

• Create a function deleteLeadingZeros() that removes the leading zeros from a number passed as a string to the function.

• Use the int() function(returns an integer from a given object) to convert the input string to an integer. This function removes all the leading zeros.

• Return the resultant number after removing all the leading 0s from the input string.

Example

The following program returns as a number that removes all the leading zeros from a number passed as a string using the int() function −

# creating a function that removes the leading zeros
# from a number passed as a string to the function
def deleteLeadingZeros(inputString):
   # converting the input string to an integer removes all the leading zeros
   result = int(inputString)
   # returning the resultant number after removing leading zeros
   return result
# input number as a string
inputString = "0002056"
print("Given String is:", inputString)
# calling the deleteLeadingZeros() function by passing the input string to it
print("After Removing Leading Zeros:", deleteLeadingZeros(inputString))

Output

On execution, the above program will generate the following output −

Given String is: 0002056
After Removing Leading Zeros: 2056

Conclusion

In this article, we learned how to remove leading zeros from a number given as a string using three different methods. We learned how to use slicing to get a subset of an iterable, such as a string, list, or tuple. We also learned how to utilize the regex module to replace (substitute) one pattern with another.