以下是我的解决方案:

def un_camel(text):
    """ Converts a CamelCase name into an under_score name. 

        >>> un_camel('CamelCase')
        'camel_case'
        >>> un_camel('getHTTPResponseCode')
        'get_http_response_code'
    """
    result = []
    pos = 0
    while pos < len(text):
        if text[pos].isupper():
            if pos-1 > 0 and text[pos-1].islower() or pos-1 > 0 and \
            pos+1 < len(text) and text[pos+1].islower():
                result.append("_%s" % text[pos].lower())
            else:
                result.append(text[pos].lower())
        else:
            result.append(text[pos])
        pos += 1
    return "".join(result)

它支持评论中讨论的那些极端情况。例如，它会像它应该的那样将getHTTPResponseCode转换为get_http_response_code。

以防有人需要转换一个完整的源文件，这里有一个脚本可以做到这一点。

# Copy and paste your camel case code in the string below
camelCaseCode ="""
    cv2.Matx33d ComputeZoomMatrix(const cv2.Point2d & zoomCenter, double zoomRatio)
    {
      auto mat = cv2.Matx33d::eye();
      mat(0, 0) = zoomRatio;
      mat(1, 1) = zoomRatio;
      mat(0, 2) = zoomCenter.x * (1. - zoomRatio);
      mat(1, 2) = zoomCenter.y * (1. - zoomRatio);
      return mat;
    }
"""

import re
def snake_case(name):
    s1 = re.sub('(.)([A-Z][a-z]+)', r'\1_\2', name)
    return re.sub('([a-z0-9])([A-Z])', r'\1_\2', s1).lower()

def lines(str):
    return str.split("\n")

def unlines(lst):
    return "\n".join(lst)

def words(str):
    return str.split(" ")

def unwords(lst):
    return " ".join(lst)

def map_partial(function):
    return lambda values : [  function(v) for v in values]

import functools
def compose(*functions):
    return functools.reduce(lambda f, g: lambda x: f(g(x)), functions, lambda x: x)

snake_case_code = compose(
    unlines ,
    map_partial(unwords),
    map_partial(map_partial(snake_case)),
    map_partial(words),
    lines
)
print(snake_case_code(camelCaseCode))

看一看优秀的Schematics库

https://github.com/schematics/schematics

它允许你创建类型化的数据结构，可以序列化/反序列化从python到Javascript风格，例如:

class MapPrice(Model):
    price_before_vat = DecimalType(serialized_name='priceBeforeVat')
    vat_rate = DecimalType(serialized_name='vatRate')
    vat = DecimalType()
    total_price = DecimalType(serialized_name='totalPrice')

我不知道为什么这些都这么复杂。

对于大多数情况，简单的表达式([A-Z]+)就可以了

>>> re.sub('([A-Z]+)', r'_\1','CamelCase').lower()
'_camel_case'  
>>> re.sub('([A-Z]+)', r'_\1','camelCase').lower()
'camel_case'
>>> re.sub('([A-Z]+)', r'_\1','camel2Case2').lower()
'camel2_case2'
>>> re.sub('([A-Z]+)', r'_\1','camelCamelCase').lower()
'camel_camel_case'
>>> re.sub('([A-Z]+)', r'_\1','getHTTPResponseCode').lower()
'get_httpresponse_code'

要忽略第一个字符，只需添加look behind (?!^)

>>> re.sub('(?!^)([A-Z]+)', r'_\1','CamelCase').lower()
'camel_case'
>>> re.sub('(?!^)([A-Z]+)', r'_\1','CamelCamelCase').lower()
'camel_camel_case'
>>> re.sub('(?!^)([A-Z]+)', r'_\1','Camel2Camel2Case').lower()
'camel2_camel2_case'
>>> re.sub('(?!^)([A-Z]+)', r'_\1','getHTTPResponseCode').lower()
'get_httpresponse_code'

如果你想分离ALLCaps到all_caps，并期望字符串中的数字，你仍然不需要做两次单独的运行，只需使用|这个表达式((?<=[a-z0-9])[A-Z]|(?!^)[A-Z](?=[A-Z]))可以处理书中的几乎所有场景

>>> a = re.compile('((?<=[a-z0-9])[A-Z]|(?!^)[A-Z](?=[a-z]))')
>>> a.sub(r'_\1', 'getHTTPResponseCode').lower()
'get_http_response_code'
>>> a.sub(r'_\1', 'get2HTTPResponseCode').lower()
'get2_http_response_code'
>>> a.sub(r'_\1', 'get2HTTPResponse123Code').lower()
'get2_http_response123_code'
>>> a.sub(r'_\1', 'HTTPResponseCode').lower()
'http_response_code'
>>> a.sub(r'_\1', 'HTTPResponseCodeXYZ').lower()
'http_response_code_xyz'

这完全取决于你想要什么，所以使用最适合你需要的解决方案，因为它不应该过于复杂。

nJoy !

没有任何库:

def camelify(out):
    return (''.join(["_"+x.lower() if i<len(out)-1 and x.isupper() and out[i+1].islower()
         else x.lower()+"_" if i<len(out)-1 and x.islower() and out[i+1].isupper()
         else x.lower() for i,x in enumerate(list(out))])).lstrip('_').replace('__','_')

有点重，但是

CamelCamelCamelCase ->  camel_camel_camel_case
HTTPRequest         ->  http_request
GetHTTPRequest      ->  get_http_request
getHTTPRequest      ->  get_http_request

在标准库中没有，但我发现这个模块似乎包含您需要的功能。