Convert to Binary and Keep Leading Zeros

Formatted string literals (f-strings)

From Python 3.6 onwards, formatted string literals, or f-strings as they are fondly called, offer a more readable syntax for string formatting:

number = 5
binary_padded = f"{number:08b}"
print(binary_padded)  # Output: '00000101', still holding strong with leading zeroes!
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Note the use of 08b here to demand an 8-digit binary number.

The Format specification mini-language

The format specification mini-language gets some serious work done when it comes to handling string formatting needs easily:

number = 5
width = 8
binary_padded = format(number, f'#0{width + 2}b')[2:]
print(binary_padded)  # Output: '00000101', without 0b shouting at your face
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It slices off the 0b prefix to present you with the nicely packed result you want.

Some attention on performance

When the objective is melting the seconds, consider using f-strings or the format function directly. Turns out they're often quicker than their predecessor, the % formatting.

Looking back at Python 2

For those nostalgic of Python 2, append 0 to your format string:

binary_padded = '{0:08b}'.format(5)
print(binary_padded)  # Compatible with Python 2.x, Output: '00000101'
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Conquering edge cases

Adaptable padding for nature's variety

When the binary length isn't written in the stars, tweak the padding:

numbers = [5, 50, 500]
binaries_padded = ['{:08b}'.format(num).rjust(max_length, '0') for num in numbers]
print(binaries_padded)  # Creates a pretty little list of 8-bit binaries, led by zeros
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Silencing the '0b' prefix elegantly

If you dislike getting into slicing wars with bin(x)[2:], tame the # option:

binary_clean = format(number, '#010b')[2:]
print(binary_clean)  // All cleaned up and '0b' removed: '00000101'
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Introducing zfill and rjust: Your new binary friends

Meet zfill and rjust, a pair of string methods ready to pad your binary strings when the road gets rough:

zfill to the rescue:

binary_zfilled = bin(5)[2:].zfill(8)
print(binary_zfilled)  // Why hello '00000101', looking filled up with zeros!
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The righteous rjust:

binary_rjusted = bin(5)[2:].rjust(8, '0')
print(binary_rjusted)  // Output: '00000101', leading the way with zeros. Way to go!
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While they both achieve the goal of padding, zfill and rjust shine in different ways.