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。

在包索引中有一个inflection库可以为您处理这些事情。在这种情况下，您将寻找inflection.underscore():

>>> inflection.underscore('CamelCase')
'camel_case'

''.join('_'+c.lower() if c.isupper() else c for c in "DeathToCamelCase").strip('_')
re.sub("(.)([A-Z])", r'\1_\2', 'DeathToCamelCase').lower()

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))

避免使用库和正则表达式:

def camel_to_snake(s):
    return ''.join(['_'+c.lower() if c.isupper() else c for c in s]).lstrip('_')

>>> camel_to_snake('ThisIsMyString')
'this_is_my_string'

就我个人而言，我不确定在python中使用正则表达式的任何东西都可以被描述为优雅。这里的大多数答案只是做“代码高尔夫”类型的RE技巧。优雅的编码应该是容易理解的。

def to_snake_case(not_snake_case):
    final = ''
    for i in xrange(len(not_snake_case)):
        item = not_snake_case[i]
        if i < len(not_snake_case) - 1:
            next_char_will_be_underscored = (
                not_snake_case[i+1] == "_" or
                not_snake_case[i+1] == " " or
                not_snake_case[i+1].isupper()
            )
        if (item == " " or item == "_") and next_char_will_be_underscored:
            continue
        elif (item == " " or item == "_"):
            final += "_"
        elif item.isupper():
            final += "_"+item.lower()
        else:
            final += item
    if final[0] == "_":
        final = final[1:]
    return final

>>> to_snake_case("RegularExpressionsAreFunky")
'regular_expressions_are_funky'

>>> to_snake_case("RegularExpressionsAre Funky")
'regular_expressions_are_funky'

>>> to_snake_case("RegularExpressionsAre_Funky")
'regular_expressions_are_funky'