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 !

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))

def convert(camel_str):
    temp_list = []
    for letter in camel_str:
        if letter.islower():
            temp_list.append(letter)
        else:
            temp_list.append('_')
            temp_list.append(letter)
    result = "".join(temp_list)
    return result.lower()

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')

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。

简洁，没有正则表达式，但HTTPResponseCode=> httpresponse_code:

def from_camel(name):
    """
    ThisIsCamelCase ==> this_is_camel_case
    """
    name = name.replace("_", "")
    _cas = lambda _x : [_i.isupper() for _i in _x]
    seq = zip(_cas(name[1:-1]), _cas(name[2:]))
    ss = [_x + 1 for _x, (_i, _j) in enumerate(seq) if (_i, _j) == (False, True)]
    return "".join([ch + "_" if _x in ss else ch for _x, ch in numerate(name.lower())])