Printing Integers in Hexadecimal Format in Python

Using hex() for basic conversion

The hex() function converts an integer to a hexadecimal string with a 0x prefix:

i = 255
print(hex(i))  # Output: 0xff

This works for negative numbers too:

print(hex(-42))  # Output: -0x2a

String formatting for control

For more control over the output, use f-strings or the format() method with format specifiers:

i = 255
print(f"Value: {i:x}")           # Output: Value: ff
print(f"Value: {i:X}")           # Output: Value: FF
print(f"Value: {i:#x}")          # Output: Value: 0xff
print(f"Value: {i:08x}")         # Output: Value: 000000ff

The format specifiers work as follows:

:x — lowercase hex without prefix
:X — uppercase hex without prefix
:#x — lowercase hex with 0x prefix
:#X — uppercase hex with 0X prefix
:08x — zero-padded to 8 characters

F-strings are the modern approach and more readable than .format():

# Older style (still works)
print("Hex: {}".format(hex(255)))

# Modern style
print(f"Hex: {255:x}")

Padding and width specifications

When working with fixed-width values like color codes or memory dumps, padding is essential:

values = [15, 255, 4095]
for val in values:
    print(f"{val:04x}")
# Output:
# 000f
# 00ff
# 0fff

Use :0Nx where N is the total width. This zero-pads on the left.

Converting hex strings back to integers

Use int() with base 16 to convert hex strings back:

hex_string = "ff"
decimal = int(hex_string, 16)
print(decimal)  # Output: 255

# Works with 0x prefix too
decimal = int("0xff", 16)
print(decimal)  # Output: 255

Practical examples

Formatting IP octets as hex:

ip_octets = [192, 168, 1, 1]
hex_ip = ".".join(f"{octet:02x}" for octet in ip_octets)
print(hex_ip)  # Output: c0.a8.01.01

Debugging binary data or memory values:

data = bytes([0x48, 0x65, 0x6c, 0x6c, 0x6f])
print(" ".join(f"{byte:02x}" for byte in data))
# Output: 48 65 6c 6c 6f

Color codes:

rgb = (255, 100, 50)
hex_color = f"#{rgb[0]:02x}{rgb[1]:02x}{rgb[2]:02x}"
print(hex_color)  # Output: #ff6432

Edge cases

For very large integers, Python handles them natively:

large = 2**64 - 1
print(f"{large:x}")  # Output: ffffffffffffffff

Negative numbers with hex formatting require caution. The format specifier applies to the magnitude, but the minus sign is prepended:

print(f"{-255:x}")    # This will raise ValueError
print(f"{-255:#x}")   # This will raise ValueError
print(hex(-255))      # Output: -0xff (use hex() instead)

If you need to handle negatives consistently, convert to unsigned (two’s complement) first if necessary, or stick with hex().