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treyhunner/walrus_oddity.py

Created November 10, 2021 16:04
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Operator precedence walrus operator oddity
Raw
walrus_oddity.py
"""
while n < 10 and chunk := f.read(256): # SyntaxError
while n < 10 and (chunk := f.read(256)): # Works
while chunk := f.read(256) and n < 10: # chunk will be a boolean 😮
"""
from io import StringIO
f = StringIO("".join(c * 256 for c in "abcdefg")) # File-like object
n = 0
chunks = []
while n < 10 and chunk := f.read(256):
chunks.append(chunk)
n += 1
assert all(type(chunk) is str for chunk in chunks)
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