micropython/tests/float/string_format_modulo2.py

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# test formatting floats with large precision, that it doesn't overflow the buffer
def test(num, num_str):
if num == float("inf") or num == 0.0 and num_str != "0.0":
# skip numbers that overflow or underflow the FP precision
return
for kind in ("e", "f", "g"):
# check precision either side of the size of the buffer (32 bytes)
for prec in range(23, 36, 2):
fmt = "%." + "%d" % prec + kind
s = fmt % num
check = abs(float(s) - num)
if num > 1:
check /= num
if check > 1e-6:
print("FAIL", num_str, fmt, s, len(s), check)
# check pure zero
test(0.0, "0.0")
# check some powers of 10, making sure to include exponents with 3 digits
for e in range(-8, 8):
num = pow(10, e)
test(num, "1e%d" % e)