[Tut] Python Int to String with Leading Zeros

[Tut] Python Int to String with Leading Zeros - Printable Version

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[Tut] Python Int to String with Leading Zeros - xSicKxBot - 11-17-2020

Python Int to String with Leading Zeros

To convert an integer

Code:
i

to a string with leading zeros so that it consists of

Code:
5

characters, use the format string

Code:
f'{i:05d}'

. The

Code:
d

flag in this expression defines that the result is a decimal value. The

Code:
str(i).zfill(5)

accomplishes the same string conversion of an integer with leading zeros.

Challenge: Given an integer number. How to convert it to a string by adding leading zeros so that the string has a fixed number of positions.

Example: For integer 42, you want to fill it up with leading zeros to the following string with 5 characters:

Code:
'00042'

.

In all methods, we assume that the integer has less than 5 characters.

Method 1: Format String

The first method uses the format string feature in Python 3+. They’re also called replacement fields.

Code:
# Integer value to be converted
i = 42 # Method 1: Format String
s1 = f'{i:05d}'
print(s1)
# 00042

The code

Code:
f'{i:05d}'

places the integer i into the newly created string. However, it tells the format language to fill the string to

Code:
5

characters with leading

Code:
'0'

s using the decimal system. This is the most Pythonic way to accomplish this challenge.

Method 2: zfill()

Another readable and Pythonic way to fill the string with leading 0s is the

Code:
string.zfill()

method.

Code:
# Method 2: zfill()
s2 = str(i).zfill(5)
print(s2)
# 00042

The method takes one argument and that is the number of positions of the resulting string. Per default, it fills with 0s.

[Image: padString-1024x576.jpg]

You can check out the following video tutorial from Finxter Adam:

Method 3: List Comprehension

Many Python coders don’t quite get the f-strings and the

Code:
zfill()

method shown in methods 2 and 3. If you don’t have time learning them, you can also use a more standard way based on string concatenation and list comprehension.

Code:
# Method 3: List Comprehension
s3 = str(i)
n = len(s3)
s3 = '0' * (5-len(s3)) + s3
print(s3)

You first convert the integer to a basic string. Then, you create the prefix of 0s you need to fill it up to

Code:
n=5

characters and concatenate it to the integer’s string representation. The asterisk operator creates a string of

Code:
5-len(s3)

zeros here.

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