Python允许从给定基数的字符串中轻松创建一个整数
int(str, base).
我想执行相反的操作:从一个整数创建一个字符串， 例如，我想要一些函数int2base(num, base)，这样:
int(int2base(x, b), b) == x
函数名/参数的顺序并不重要。
对于int()将接受的任何以b为底的数字x。
这是一个很容易写的函数:事实上，它比在这个问题中描述它更容易。然而，我觉得我一定是错过了什么。
我知道函数bin, oct, hex，但我不能使用它们的几个原因:
这些函数在旧版本的Python中不可用，我需要与(2.2)兼容 我想要一个通解对于不同的碱都可以用同样的方式表示 我想允许2 8 16以外的底数
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当前回答
我让函数这样做。在windows 10, python 3.7.3上运行良好。
def number_to_base(number, base, precision = 10):
if number == 0:
return [0]
positive = number >= 0
number = abs(number)
ints = [] # store the integer bases
floats = [] # store the floating bases
float_point = number % 1
number = int(number)
while number:
ints.append(int(number%base))
number //= base
ints.reverse()
while float_point and precision:
precision -= 1
float_point *= base
floats.append(int(float_point))
float_point = float_point - int(float_point)
return ints, floats, positive
def base_to_str(bases, string="0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"):
"""bases is a two dimension list, where bases[0] contains a list of the integers,
and bases[1] contains a list of the floating numbers, bases[2] is a boolean, that's
true when it's a positive number
"""
ints = []
floats = []
for i in bases[0]:
ints.append(string[i])
for i in bases[1]:
floats.append(string[i])
if len(bases[1]) > 0:
return (["-", ""][bases[2]] + "".join(ints)) + "." + ("".join(floats))
else:
return (["-", ""][bases[2]] + "".join(ints))
例子:
>>> base_to_str(number_to_base(-6.252, 2))
'-110.0100000010'
其他回答
def dec_to_radix(input, to_radix=2, power=None):
if not isinstance(input, int):
raise TypeError('Not an integer!')
elif power is None:
power = 1
if input == 0:
return 0
else:
remainder = input % to_radix**power
digit = str(int(remainder/to_radix**(power-1)))
return int(str(dec_to_radix(input-remainder, to_radix, power+1)) + digit)
def radix_to_dec(input, from_radix):
if not isinstance(input, int):
raise TypeError('Not an integer!')
return sum(int(digit)*(from_radix**power) for power, digit in enumerate(str(input)[::-1]))
def radix_to_radix(input, from_radix=10, to_radix=2, power=None):
dec = radix_to_dec(input, from_radix)
return dec_to_radix(dec, to_radix, power)
很棒的答案! 我想我问题的答案是“不”，我并没有错过一些明显的解决方案。 下面是我将使用的函数，它可以浓缩答案中所表达的好想法。
允许调用者提供的字符映射(允许base64编码) 检查负数和零 将复数映射为字符串元组
def int2base(x,b,alphabet='0123456789abcdefghijklmnopqrstuvwxyz'): 'convert an integer to its string representation in a given base' if b<2 or b>len(alphabet): if b==64: # assume base64 rather than raise error alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/" else: raise AssertionError("int2base base out of range") if isinstance(x,complex): # return a tuple return ( int2base(x.real,b,alphabet) , int2base(x.imag,b,alphabet) ) if x<=0: if x==0: return alphabet[0] else: return '-' + int2base(-x,b,alphabet) # else x is non-negative real rets='' while x>0: x,idx = divmod(x,b) rets = alphabet[idx] + rets return rets
下面是一个如何将任意基数转换为另一个基数的示例。
from collections import namedtuple
Test = namedtuple("Test", ["n", "from_base", "to_base", "expected"])
def convert(n: int, from_base: int, to_base: int) -> int:
digits = []
while n:
(n, r) = divmod(n, to_base)
digits.append(r)
return sum(from_base ** i * v for i, v in enumerate(digits))
if __name__ == "__main__":
tests = [
Test(32, 16, 10, 50),
Test(32, 20, 10, 62),
Test(1010, 2, 10, 10),
Test(8, 10, 8, 10),
Test(150, 100, 1000, 150),
Test(1500, 100, 10, 1050000),
]
for test in tests:
result = convert(*test[:-1])
assert result == test.expected, f"{test=}, {result=}"
print("PASSED!!!")
我让函数这样做。在windows 10, python 3.7.3上运行良好。
def number_to_base(number, base, precision = 10):
if number == 0:
return [0]
positive = number >= 0
number = abs(number)
ints = [] # store the integer bases
floats = [] # store the floating bases
float_point = number % 1
number = int(number)
while number:
ints.append(int(number%base))
number //= base
ints.reverse()
while float_point and precision:
precision -= 1
float_point *= base
floats.append(int(float_point))
float_point = float_point - int(float_point)
return ints, floats, positive
def base_to_str(bases, string="0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"):
"""bases is a two dimension list, where bases[0] contains a list of the integers,
and bases[1] contains a list of the floating numbers, bases[2] is a boolean, that's
true when it's a positive number
"""
ints = []
floats = []
for i in bases[0]:
ints.append(string[i])
for i in bases[1]:
floats.append(string[i])
if len(bases[1]) > 0:
return (["-", ""][bases[2]] + "".join(ints)) + "." + ("".join(floats))
else:
return (["-", ""][bases[2]] + "".join(ints))
例子:
>>> base_to_str(number_to_base(-6.252, 2))
'-110.0100000010'
我提出了一个“非优化”的2到9基的解决方案:
def to_base(N, base=2):
N_in_base = ''
while True:
N_in_base = str(N % base) + N_in_base
N //= base
if N == 0:
break
return N_in_base
这个解决方案不需要反转最终结果，但实际上并没有优化。请参考以下答案了解原因:https://stackoverflow.com/a/37133870/7896998
