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

相关的

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当前回答

令人惊讶的是,人们给出的答案只能转换成小基数(比英语字母表的长度还小)。没有人试图给出一个可以转换为2到无穷任意底数的解。

这里有一个超级简单的解决方案:

def numberToBase(n, b):
    if n == 0:
        return [0]
    digits = []
    while n:
        digits.append(int(n % b))
        n //= b
    return digits[::-1]

所以如果你需要把一个超级大的数转换成577的底数,

numberToBase(67854 ** 15 - 102,577),将为您提供正确的解决方案: [4, 473, 131, 96, 431, 285, 524, 486, 28, 23, 16, 82, 292, 538, 149, 25, 41, 483, 100, 517, 131, 28, 0, 435, 197, 264, 455],

你以后可以把它转换成任何你想要的基数

at some point of time you will notice that sometimes there is no built-in library function to do things that you want, so you need to write your own. If you disagree, post you own solution with a built-in function which can convert a base 10 number to base 577. this is due to lack of understanding what a number in some base means. I encourage you to think for a little bit why base in your method works only for n <= 36. Once you are done, it will be obvious why my function returns a list and has the signature it has.

其他回答

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'

我个人使用我写的这个函数

import string

def to_base(value, base, digits=string.digits+string.ascii_letters):    # converts decimal to base n

    digits_slice = digits[0:base]

    temporary_var = value
    data = [temporary_var]

    while True:
        temporary_var = temporary_var // base
        data.append(temporary_var)
        if temporary_var < base:
            break

    result = ''
    for each_data in data:
        result += digits_slice[each_data % base]
    result = result[::-1]

    return result

你可以这样使用它

基础= 2)打印(to_base(7日)

输出: “111”

基础= 3)打印(to_base(23日)

输出: “212”

请随时对我的代码提出改进建议。

我为此做了一个小包裹。

我建议你使用我的bases.py https://github.com/kamijoutouma/bases.py,它的灵感来自于bases.js

from bases import Bases
bases = Bases()

bases.toBase16(200)                // => 'c8'
bases.toBase(200, 16)              // => 'c8'
bases.toBase62(99999)              // => 'q0T'
bases.toBase(200, 62)              // => 'q0T'
bases.toAlphabet(300, 'aAbBcC')    // => 'Abba'

bases.fromBase16('c8')               // => 200
bases.fromBase('c8', 16)             // => 200
bases.fromBase62('q0T')              // => 99999
bases.fromBase('q0T', 62)            // => 99999
bases.fromAlphabet('Abba', 'aAbBcC') // => 300

参考https://github.com/kamijoutouma/bases.py#known-basesalphabets 哪些基是可用的

编辑: PIP link https://pypi.python.org/pypi/bases.py/0.2.2

我写了这个函数,我用它来编码不同的碱基。我还提供了通过值“offset”来移动结果的方法。如果你想编码到64进制以上,但保持可显示字符(如95进制),这是有用的。

我还试图避免反转输出“列表”,并尽量减少计算操作。pow(base)数组是根据需要计算的,并保留用于对函数的其他调用。

输出是一个二进制字符串

pows = {}

######################################################
def encode_base(value,
                base = 10,
                offset = 0) :

    """
    Encode value into a binary string, according to the desired base.

    Input :
        value : Any positive integer value
        offset : Shift the encoding (eg : Starting at chr(32))
        base : The base in which we'd like to encode the value

    Return : Binary string

    Example : with : offset = 32, base = 64

              100 -> !D
              200 -> #(
    """

    # Determine the number of loops
    try :
        pb = pows[base]

    except KeyError :
        pb = pows[base] = {n : base ** n for n in range(0, 8) if n < 2 ** 48 -1}

    for n in pb :
        if value < pb[n] :
            n -= 1
            break

    out = []
    while n + 1 :
        b = pb[n]
        out.append(chr(offset + value // b))
        n -= 1
        value %= b

    return ''.join(out).encode()

简单基底变换

def int_to_str(x, b):
    s = ""
    while x:
        s = str(x % b) + s
        x //= b
    return s

输出的例子,没有0到基数9

s = ""
x = int(input())
while x:
    if x % 9 == 0:
        s = "9" + s
        x -= x % 10
        x = x // 9
    else:
        s = str(x % 9) + s
        x = x // 9

print(s)