from re import search, IGNORECASE

def is_string_match(word1, word2):
    #  Case insensitively function that checks if two words are the same
    # word1: string
    # word2: string | list

    # if the word1 is in a list of words
    if isinstance(word2, list):
        for word in word2:
            if search(rf'\b{word1}\b', word, IGNORECASE):
                return True
        return False

    # if the word1 is same as word2
    if search(rf'\b{word1}\b', word2, IGNORECASE):
        return True
    return False

is_match_word = is_string_match("Hello", "hELLO") 
True

is_match_word = is_string_match("Hello", ["Bye", "hELLO", "@vagavela"])
True

is_match_word = is_string_match("Hello", "Bye")
False

通常的方法是将字符串大写或小写，以便进行查找和比较。例如:

>>> "hello".upper() == "HELLO".upper()
True
>>> 

Unicode标准的第3.13节定义了无大小写的算法 匹配。

X.casefold() == Python 3中的Y.casefold()实现了“默认的无大小写匹配”(D144)。

案例折叠不会在所有实例中保存字符串的规范化，因此需要进行规范化('å' vs。“一个”)。D145引入了“规范无大小写匹配”:

import unicodedata

def NFD(text):
    return unicodedata.normalize('NFD', text)

def canonical_caseless(text):
    return NFD(NFD(text).casefold())

对于涉及U+0345字符的非常罕见的边缘情况，NFD()被调用两次。

例子:

>>> 'å'.casefold() == 'å'.casefold()
False
>>> canonical_caseless('å') == canonical_caseless('å')
True

此外，还有兼容无案例匹配(D146)，如“mhz”(U+3392)和“标识符无案例匹配”，以简化和优化标识符的无案例匹配。

from re import search, IGNORECASE

def is_string_match(word1, word2):
    #  Case insensitively function that checks if two words are the same
    # word1: string
    # word2: string | list

    # if the word1 is in a list of words
    if isinstance(word2, list):
        for word in word2:
            if search(rf'\b{word1}\b', word, IGNORECASE):
                return True
        return False

    # if the word1 is same as word2
    if search(rf'\b{word1}\b', word2, IGNORECASE):
        return True
    return False

is_match_word = is_string_match("Hello", "hELLO") 
True

is_match_word = is_string_match("Hello", ["Bye", "hELLO", "@vagavela"])
True

is_match_word = is_string_match("Hello", "Bye")
False

考虑使用jaraco.text中的FoldedCase:

>>> from jaraco.text import FoldedCase
>>> FoldedCase('Hello World') in ['hello world']
True

如果你想要一个不考虑大小写的字典，使用来自jaraco.collections的FoldedCaseKeyedDict:

>>> from jaraco.collections import FoldedCaseKeyedDict
>>> d = FoldedCaseKeyedDict()
>>> d['heLlo'] = 'world'
>>> list(d.keys()) == ['heLlo']
True
>>> d['hello'] == 'world'
True
>>> 'hello' in d
True
>>> 'HELLO' in d
True

假设ASCII字符串:

string1 = 'Hello'
string2 = 'hello'

if string1.lower() == string2.lower():
    print("The strings are the same (case insensitive)")
else:
    print("The strings are NOT the same (case insensitive)")

从Python 3.3开始，casefold()是一个更好的选择:

string1 = 'Hello'
string2 = 'hello'

if string1.casefold() == string2.casefold():
    print("The strings are the same (case insensitive)")
else:
    print("The strings are NOT the same (case insensitive)")

如果您想要一个处理更复杂unicode比较的更全面的解决方案，请参阅其他答案。