Adding leading zeros in python

Python How to Add Leading Zeros: Methods and Examples

Learn the different methods for adding leading zeros in Python, including zfill(), rjust(), format(), and Pandas’ DataFrame methods. Improve your Python code functionality with these examples.

• Using zfill() to add leading zeros
• Using rjust() to add leading zeros
• Insert Leading Zeros In Python
• Using format() to add leading zeros
• Converting a string to a number and using the above methods
• Adding leading zeros in a DataFrame using Pandas
• Other helpful code examples for adding leading zeros in Python
• Conclusion
• How do you include leading zeros in Python?
• How do you add a leading zero to a string?
• Why leading zero is not allowed in Python?

Python is a versatile programming language used for a variety of applications, including web development, scientific computing, and data analysis. Adding leading zeros to a string or number is a common task in Python. There are several ways to accomplish this, and in this blog post, we will explore different methods for adding leading zeros in Python, including zfill(), rjust(), format(), and str().

Using zfill() to add leading zeros

zfill() is a built-in Python method that pads a string with zeros on the left until the desired width is reached. This method takes an integer argument, which specifies the width of the final string. If the original string is shorter than the specified width, it is padded with zeros to the left.

num = '5' num = num.zfill(2) print(num) 

In the above example, the original string ‘5’ is padded with a zero to make it a two-digit string.

Using rjust() to add leading zeros

rjust() is another built-in Python method that adds padding to the left side of a string. This method takes two arguments, the first one is the width of the final string, and the second argument is the character to use for padding. By default, the padding character is a space.

num = '5' num = num.rjust(2, '0') print(num) 

In the above example, the original string ‘5’ is padded with a zero to make it a two-digit string.

Insert Leading Zeros In Python

How to insert leading zeros in python .▻ Buy Me a Coffee? Your support is much appreciated! Duration: 1:35

Using format() to add leading zeros

format() is a method that can be used to pad numbers with leading zeros. This method takes a format string as an argument, which specifies the width of the final string and the padding character. The format string uses the syntax ‘’, where width is the width of the final string, and padding is the character to use for padding.

num = 5 num = ''.format(num) print(num) 

In the above example, the number 5 is converted to a string and padded with a zero to make it a two-digit string.

Converting a string to a number and using the above methods

To add leading zeros to a string, you can convert it to a number using int() or float() and then use the above methods.

num = '5' num = int(num) num = ''.format(num) print(num) 

In the above example, the string ‘5’ is converted to an integer and padded with a zero to make it a two-digit string.

Adding leading zeros in a DataFrame using Pandas

Pandas offers methods for adding leading zeros to strings and numbers in a DataFrame. The apply() method can be used to apply a function to each element of a DataFrame column.

import pandas as pd df = pd.DataFrame() df['num'] = df['num'].apply(lambda x: ''.format(x)) print(df) 

num
0	05
1	10
2	15

In the above example, a DataFrame is created with a column ’num’ containing integers. The apply() method is used to apply a lambda function to each element of the column. The lambda function formats each element with leading zeros and returns the result.

Other helpful code examples for adding leading zeros in Python

In python, python convert number to string with leading zeros code example

str(1).zfill(2) # 1 will be '01'str(23).zfill(4) # 23 will be '0023'

In python, python add zero to string code example

# add zeros in front of a string >>> n = '4' >>> print(n.zfill(3)) 004

# add zeros to numbers >>> n = 4 >>> print(f'') # Preferred method, python >= 3.6 004 >>> print('%03d' % n) 004 >>> print(format(n, '03')) # python >= 2.6 004 >>> print(''.format(n)) # python >= 2.6 + python 3 004 >>> print(''.format(foo=n)) # python >= 2.6 + python 3 004 >>> print(''.format(n)) # python >= 2.7 + python3 004

Conclusion

Adding leading zeros to a string or number is a common task in Python, and there are several ways to accomplish this. zfill(), rjust(), format(), and Pandas’ DataFrame methods are all effective methods for adding leading zeros. By using these methods, you can easily add leading zeros to your Python code and improve its functionality.

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Adding leading zeros in python

Last updated: Feb 19, 2023
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# Table of Contents

# Add leading zeros to a number in Python

To add leading zeros to a number:

1. Use the str() class to convert the number to a string.
2. Use the str.zfill() method to add leading zeros to the string.
3. The method takes the width of the string and pads it with leading zeros.

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num = 246 result_1 = str(num).zfill(5) print(result_1) # 👉️ '00246' result_2 = str(num).zfill(6) print(result_2) # 👉️ '000246' 

We used the str() class to convert the number to a string.

This is necessary because adding leading zeros to a number causes a SyntaxError .

The str.zfill method takes the width of the string and left-fills the string with 0 digits to make it of the specified width.

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num = 13 result_1 = str(num).zfill(3) print(result_1) # 👉️ '013' result_2 = str(num).zfill(4) print(result_2) # 👉️ '0013' 

Converting the number 13 to a string gives us a string with a length of 2 .

Passing 3 as the width to the zfill() method means that the string will get left-filled with a single 0 digit.

# The zfill() method handles the leading sign prefix

The str.zfill() method handles a leading sign prefix (e.g. + or — ) by inserting the padding after the sign.

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num = -13 result_1 = str(num).zfill(3) print(result_1) # 👉️ '-13' result_2 = str(num).zfill(4) print(result_2) # 👉️ '-013' 

Note that the sign counts toward the width of the string.

If the specified width is less than or equal to the length of the original string, then the original string is returned.

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num = 13 result_1 = str(num).zfill(2) print(result_1) # 👉️ '13' result_2 = str(num).zfill(1) print(result_2) # 👉️ '13' 

The number in the example has a length of 2 , so trying to fill it to 2 characters doesn’t have an effect.

# Using a formatted string literal to add leading zeros to a number

Alternatively, you can use a formatted string literal to add leading zeros to a number.

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num = 13 result_1 = f'num:04>' print(result_1) # 👉️ '0013' result_2 = f'num:05>' print(result_2) # 👉️ '00013' 

We don’t have to use the str() class to convert the integer to a string as the conversion is done for us automatically.

Formatted string literals (f-strings) let us include expressions inside of a string by prefixing the string with f .

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my_str = 'is subscribed:' my_bool = True result = f'my_str> my_bool>' print(result) # 👉️ is subscribed: True 

Make sure to wrap expressions in curly braces — .

Formatted string literals also enable us to use the format specification mini-language in expression blocks.

The first digit after the colon is the fill value and the second is the width of the string.

Copied! 
num = 13 result_1 = f'num:04>' print(result_1) # 👉️ '0013' 

This approach also works if the width of the string is stored in a variable.

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num = 13 width_of_string = 4 result_1 = f'num:0width_of_string>>' print(result_1) # 👉️ '0013' 

# Add leading zeros to a number using str.format()

You can also use the str.format() method to add leading zeros to a number.

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num = 13 result_1 = ''.format(num) print(result_1) # 👉️ '0013' result_2 = ''.format(num) print(result_2) # 👉️ '00013' 

The str.format method performs string formatting operations.

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first = 'bobby' last = 'hadz' result = "Name: <> <>".format(first, last) print(result) # 👉️ "Name: bobby hadz" 

The string the method is called on can contain replacement fields specified using curly braces <> .

# Add leading zeros to a number using str.rjust()

You can also use the str.rjust() method to add leading zeros to a number.

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num = 13 result_1 = str(num).rjust(4, '0') print(result_1) # 👉️ '0013' result_2 = str(num).rjust(5, '0') print(result_2) # 👉️ '00013' 

The str.rjust method pads the beginning of the string to the specified width with the provided fill character.

The str.rjust method takes the following 2 arguments:

Name	Description
width	The total length of the padded string
fillchar	The fill character to pad the string with

Copied! 
num = 13 result_1 = str(num).rjust(4, '0') print(result_1) # 👉️ '0013' 

The first argument is the width of the padded string and the second is the fill character ( 0 in our case).

Notice that we had to convert the number to a string using the str() class.

This is necessary because rjust() is a method implemented on strings.

# Add leading zeros to a number using format()

You can also use the format() function to add leading zeros to a number.

Copied! 
num = 13 result = format(num, '03') print(result) # 👉️ 013 result = format(num, '04') print(result) # 👉️ 0013 result = format(num, '05') print(result) # 👉️ 00013 

The first argument the format() function takes is the value and the second is a string used to format the value.

The first digit is the fill character ( 0 ) and the second is the total width of the string.

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