Python Note - 02

str, byte, int转换

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x = int("43")
y = int("0xff", 16)

而使用base = 0可以自动探测前缀：

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x = int("0x43", 0)      # 67
y = int("43", 0)        # 43

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s1 = int(63)    # "63"
s2 = hex(48)    # "0x30"
s3 = bin(15)    # "0b1111"
s4 = oct(10)    # "0o12"

另外可以使用自定义的base format:

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format(255, "x")
# "ff"
format(255, "#x")
# "0x42"
format(255, "X")
# "FF"
format(255, "#X")
# "0XFF"
format(66, "b")
# "1000010"
format(66, "#b")
# "0b1000010"
format(66, "o")
# "102"
format(66, "#o")
# "0o102"
format(66, "d")
# "66"

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n = 0x12345678
b1 = n.to_bytes(4, "big")
print(b1)
# b'\x12\x34\x56\x78'
b2 = n.to_bytes(4, "little")
print(b2)
# b'\x78\x56\x34\x12'

int.from_bytes

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b = b"\x78\x56\x34\x12"
n = int.from_bytes(b, "little")
print(hex(n))
# 0x12345678

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hex_s = "41424344"
b = bytes.fromhex(hex_s)
print(b)
# b'ABCD'

注意可以用removeprefix来删除字符的前缀:

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hex_s = "0x41424344"
b = bytes.fromhex(hex_s.removeprefix("0x"))
print(b)
# b'ABCD'

str.hex()

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b = b"ABCD"
hex_s = b.hex()
print(hex_s)
# 41424344