Besides going through string formatting, it is interesting to have in mind that when working with numbers and their hexadecimal representation we usually are dealing with byte-content, and interested in how bytes relate.
The bytes class in Python 3 had been enriched with methods over the 3.x series, and int.to_bytes combined with the bytes.hex[] provide full control of the hex-digits output, while preserving the semantics of the transform [not to mention, holding the
intermediate "bytes" object ready to be used in any binary protocol that requires the number]:
In [8]: i = 3735928559
In [9]: i.to_bytes[4, "big"].hex[]
Out[9]: 'deadbeef'
Besides that, bytes.hex[] allow some control over the output, such as specifying a separator for the hex digits:
In [10]: bytes.hex?
Docstring:
Create a string of hexadecimal numbers from a bytes object.
sep
An optional single character or byte to separate hex bytes.
bytes_per_sep
How many bytes between separators. Positive values count from the
right, negative values count from the left.
Example:
>>> value = b'\xb9\x01\xef'
>>> value.hex[]
'b901ef'
>>> value.hex[':']
'b9:01:ef'
>>> value.hex[':', 2]
'b9:01ef'
>>> value.hex[':', -2]
'b901:ef'
[That said, in most scenarios just a quick print is wanted, I'd probably just go through f-string formatting, as in the accepted answer: f"{mynumber:04x}" - for the simple reason of "less things to remember"]
- Problem Formulation
- Method 1: Slicing
- Method 2: Slicing + zfill[]
- Method 3: Negative Hex Numbers
- Where to Go From Here?
- Programming Humor
Problem Formulation
If you print a hexadecimal number, Python uses the prefix '0x' to indicate that
it’s a number in the hexadecimal system and not in the decimal system like normal integers.
print[hex[42]] # 0x2a
However, if you already know that the output numbers are hexadecimal, you don’t necessarily need the '0x' prefix.
How to print hex numbers without the '0x' prefix?
Method 1: Slicing
To
skip the prefix, use slicing and start with index 2 on the hexadecimal string. For example, to skip the prefix '0x' on the result of x = hex[42] ='0x2a', use the slicing operation x[2:] that results in just the hexadecimal number '2a' without the prefix '0x'.
x = hex[42] print[x] # 0x2a print[x[2:]] # 2a
Feel free to dive into the hex[] built-in function in this video tutorial:
Python hex[] Function – Not a Magic Trick
But what if you actually want to replace the prefix '0x' with the prefix '00' so that the resulting string has the same length?
Method 2: Slicing + zfill[]
The
Python string.zfill[] method fills the string from the left with '0' characters. In combination with slicing from the third character, you can easily construct a hexadecimal string without leading '0x' characters and with leading '0' characters up to the length passed into the string.zfill[length] method.
print[hex[42][2:].zfill[4]] # 002a
Alternatively, if you want to create a string with 8 characters, use string.zfill[8]:
print[hex[42][2:].zfill[8]] # 0000002a
You can learn more about zfill[] in this video about
Python string methods:
Python String Methods [Ultimate Guide]
Method 3: Negative Hex Numbers
If you need to handle negative hexadecimal numbers, the above methods do not work because the hex number now needs to replace the second and third character '0x'. For example, the hexadecimal number hex[-42] is '-0x2a'. You cannot simply skip the first two characters to obtain the
correct result, can you? At the same time, if you always skipped or replaced the second and third characters, it wouldn’t work for positive numbers either. So what to do?
To print a positive or negative hexadecimal without the '0x' or '-0x' prefixes, you can simply use the string.replace['x', '0'] method and replace each occurrence of 'x' with '0'. The resulting string is
mathematically correct because leading '0's don’t change the value of the number.
# Negative Hexadecimal print[hex[-42].replace['x', '0']] # -002a # Positive Hexadecimal print[hex[42].replace['x', '0']] # 002a
Where to Go From Here?
Enough theory. Let’s get some practice!
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Programming Humor
While working as a researcher in distributed systems, Dr. Christian Mayer found his love for teaching computer science students.
To help students reach higher levels of Python success, he founded the programming education website Finxter.com. He’s author of the popular programming book Python One-Liners [NoStarch 2020], coauthor of the Coffee Break Python series of self-published books, computer science enthusiast, freelancer, and owner of one of the top 10 largest Python blogs worldwide.
His passions are writing, reading, and coding. But his greatest passion is to serve aspiring coders through Finxter and help them to boost their skills. You can join his free email academy here.