参见Python PEP 8:函数和变量名:

函数名应该是小写的，单词之间用下划线分隔，以提高可读性。 变量名遵循与函数名相同的约定。 mixedCase只允许在已经是流行风格的上下文中使用(例如threading.py)，以保持向后兼容性。

There is PEP 8, as other answers show, but PEP 8 is only the styleguide for the standard library, and it's only taken as gospel therein. One of the most frequent deviations of PEP 8 for other pieces of code is the variable naming, specifically for methods. There is no single predominate style, although considering the volume of code that uses mixedCase, if one were to make a strict census one would probably end up with a version of PEP 8 with mixedCase. There is little other deviation from PEP 8 that is quite as common.

有一篇关于这方面的论文:http://www.cs.kent.edu/~jmaletic/papers/ICPC2010-CamelCaseUnderScoreClouds.pdf

它说snake_case比camelCase可读性更好。这就是为什么现代语言在任何可能的地方都使用(或应该使用)蛇。

编码风格通常是组织内部策略/约定标准的一部分，但我认为一般来说，all_lower_case_underscore_separator风格(也称为snake_case)在python中最常见。

如前所述，PEP 8要求对变量、方法和函数使用lower_case_with_下划线。

我更喜欢使用lower_case_with_下划线的变量和mixedCase的方法和函数，使代码更显式和可读。因此，遵循Python的“显式优于隐式”和“可读性很重要”的禅意。

无论是否在课堂上或在课堂外:

变量和函数小写，如下所示:

name = "John"

def display(name):
    print("John")

如果它们多于一个单词，则用下划线“_”分隔，如下所示:

first_name = "John"

def display_first_name(first_name):
    print(first_name)

并且，如果一个变量是一个常量，它是大写的，如下所示:

FIRST_NAME = "John"