骆驼案变蛇案

import re

name = 'CamelCaseName'
name = re.sub(r'(?<!^)(?=[A-Z])', '_', name).lower()
print(name)  # camel_case_name

如果你这样做了很多次，上面的速度很慢，提前编译正则表达式:

pattern = re.compile(r'(?<!^)(?=[A-Z])')
name = pattern.sub('_', name).lower()

为了处理更高级的情况(这是不可逆的了):

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

print(camel_to_snake('camel2_camel2_case'))  # camel2_camel2_case
print(camel_to_snake('getHTTPResponseCode'))  # get_http_response_code
print(camel_to_snake('HTTPResponseCodeXYZ'))  # http_response_code_xyz

添加带有两个或两个以上下划线的also大小写:

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

斯内克案转帕斯卡案

name = 'snake_case_name'
name = ''.join(word.title() for word in name.split('_'))
print(name)  # SnakeCaseName

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())])

一个使用正则表达式的可怕例子(你可以很容易地清理:)):

def f(s):
    return s.group(1).lower() + "_" + s.group(2).lower()

p = re.compile("([A-Z]+[a-z]+)([A-Z]?)")
print p.sub(f, "CamelCase")
print p.sub(f, "getHTTPResponseCode")

但适用于getHTTPResponseCode !

或者，使用lambda:

p = re.compile("([A-Z]+[a-z]+)([A-Z]?)")
print p.sub(lambda x: x.group(1).lower() + "_" + x.group(2).lower(), "CamelCase")
print p.sub(lambda x: x.group(1).lower() + "_" + x.group(2).lower(), "getHTTPResponseCode")

编辑:对于像“Test”这样的情况，应该也很容易看到有改进的空间，因为下划线是无条件插入的。

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()

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()