Python 3, 26 bytes

print('abc'[::-(1/2>0)|1])

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Python 2, 26 bytes

print('abc'[::-(1/2>0)|1])

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25-byte version with exit instead, which outputs to STDERR instead.

Python 3, 26 bytes

print('abc'[::-(1/2>0)|1])

Try it online!

Python 2, 26 bytes

print('abc'[::-(1/2>0)|1])

Try it online!

25-byte version with exit instead, which outputs to STDERR instead.

This is basically the same as print('abc'[::[1,-1][1/2>0]]), just that it's golfed.

Python 2, 27 bytes

print('abc'[::-(1/2==0)|1])

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Python 3, 27 bytes

print('abc'[::-(1/2==0)|1])

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Python 3, 26 bytes

print('abc'[::-(1/2>0)|1])

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Python 2, 26 bytes

print('abc'[::-(1/2>0)|1])

Try it online!

25-byte version with exit instead, which outputs to STDERR instead.