{"id":1056125,"date":"2024-12-31T14:56:57","date_gmt":"2024-12-31T06:56:57","guid":{"rendered":"https:\/\/docs.pingcode.com\/ask\/ask-ask\/1056125.html"},"modified":"2024-12-31T14:56:59","modified_gmt":"2024-12-31T06:56:59","slug":"%e5%9c%a8python%e8%af%ad%e8%a8%80%e4%b8%ad%e7%a9%ba%e5%80%bc%e5%a6%82%e4%bd%95%e8%a1%a8%e7%a4%ba","status":"publish","type":"post","link":"https:\/\/docs.pingcode.com\/ask\/1056125.html","title":{"rendered":"\u5728python\u8bed\u8a00\u4e2d\u7a7a\u503c\u5982\u4f55\u8868\u793a"},"content":{"rendered":"

\"\u5728python\u8bed\u8a00\u4e2d\u7a7a\u503c\u5982\u4f55\u8868\u793a\"<\/p>\n

\u5728Python\u8bed\u8a00\u4e2d\uff0c\u7a7a\u503c\u901a\u5e38\u7528None<\/code>\u6765\u8868\u793a\u3002None<\/code>\u662fPython\u4e2d\u7684\u4e00\u4e2a\u7279\u6b8a\u5e38\u91cf\uff0c\u7528\u4e8e\u8868\u793a\u7a7a\u503c\u3001\u672a\u8d4b\u503c\u3001\u7f3a\u5931\u503c\u548c\u9ed8\u8ba4\u503c<\/strong>\u3002\u5b83\u662f\u4e00\u4e2a\u5bf9\u8c61\uff0c\u5e76\u4e14\u5728\u5168\u5c40\u8303\u56f4\u5185\u552f\u4e00\u5b58\u5728\u3002None<\/code>\u5728\u5e03\u5c14\u4e0a\u4e0b\u6587\u4e2d\u88ab\u89e3\u91ca\u4e3aFalse<\/code>\uff0c\u5e76\u4e14\u901a\u5e38\u7528\u4e8e\u521d\u59cb\u5316\u53d8\u91cf\u3001\u4f5c\u4e3a\u51fd\u6570\u7684\u9ed8\u8ba4\u53c2\u6570\u503c\u548c\u8868\u793a\u7f3a\u5931\u6216\u672a\u8d4b\u503c\u7684\u72b6\u6001\u3002\u4ee5\u4e0b\u662f\u5173\u4e8ePython\u4e2d\u7a7a\u503c\u7684\u8be6\u7ec6\u4ecb\u7ecd\u3002<\/p>\n<\/p>\n

\u4e00\u3001None<\/code>\u7684\u4f7f\u7528<\/h3>\n<\/p>\n

1\u3001\u521d\u59cb\u5316\u53d8\u91cf<\/h4>\n<\/p>\n

\u5728Python\u4e2d\uff0c\u53ef\u4ee5\u4f7f\u7528None<\/code>\u6765\u521d\u59cb\u5316\u53d8\u91cf\uff0c\u8868\u793a\u8be5\u53d8\u91cf\u5c1a\u672a\u88ab\u8d4b\u4e88\u5b9e\u9645\u7684\u503c\u3002\u4f8b\u5982\uff1a<\/p>\n<\/p>\n

my_variable = None<\/p>\n
<\/code><\/pre>\n<\/p>\n
\u8fd9\u6837\u505a\u7684\u76ee\u7684\u662f\u4e3a\u4e86\u5728\u4ee3\u7801\u540e\u7eed\u90e8\u5206\u4e2d\u5bf9\u8be5\u53d8\u91cf\u8fdb\u884c\u8d4b\u503c\u3002<\/p>\n<\/p>\n
2\u3001\u51fd\u6570\u7684\u9ed8\u8ba4\u53c2\u6570\u503c<\/h4>\n<\/p>\n
\u5728\u5b9a\u4e49\u51fd\u6570\u65f6\uff0c\u53ef\u4ee5\u4f7f\u7528None<\/code>\u4f5c\u4e3a\u51fd\u6570\u53c2\u6570\u7684\u9ed8\u8ba4\u503c\u3002\u5f53\u8c03\u7528\u51fd\u6570\u65f6\uff0c\u5982\u679c\u672a\u63d0\u4f9b\u76f8\u5e94\u7684\u53c2\u6570\uff0c\u53c2\u6570\u7684\u503c\u5c06\u4f1a\u662fNone<\/code>\u3002\u4f8b\u5982\uff1a<\/p>\n<\/p>\n
def my_function(param=None):<\/p>\n
    if param is None:<\/p>\n
        param = "default value"<\/p>\n
    print(param)<\/p>\n
<\/code><\/pre>\n<\/p>\n
\u8fd9\u6837\u53ef\u4ee5\u6709\u6548\u5730\u5904\u7406\u51fd\u6570\u53c2\u6570\u7684\u7f3a\u7701\u60c5\u51b5\u3002<\/p>\n<\/p>\n
3\u3001\u8868\u793a\u7f3a\u5931\u503c\u6216\u672a\u8d4b\u503c<\/h4>\n<\/p>\n
\u5728\u5904\u7406\u6570\u636e\u65f6\uff0c\u5982\u679c\u67d0\u4e2a\u503c\u7f3a\u5931\u6216\u5c1a\u672a\u8d4b\u503c\uff0c\u53ef\u4ee5\u4f7f\u7528None<\/code>\u6765\u8868\u793a\u3002\u4f8b\u5982\uff0c\u5728\u5904\u7406\u6570\u636e\u8868\u65f6\uff0c\u5982\u679c\u67d0\u4e2a\u5355\u5143\u683c\u6ca1\u6709\u503c\uff0c\u53ef\u4ee5\u7528None<\/code>\u6765\u8868\u793a\uff1a<\/p>\n<\/p>\n
data = {'name': 'John', 'age': None}<\/p>\n
<\/code><\/pre>\n<\/p>\n
\u4e8c\u3001None<\/code>\u7684\u7279\u6027<\/h3>\n<\/p>\n
1\u3001\u552f\u4e00\u6027<\/h4>\n<\/p>\n
None<\/code>\u662f\u4e00\u4e2a\u5355\u4f8b\u5bf9\u8c61\uff0c\u8fd9\u610f\u5473\u7740\u5728\u6574\u4e2aPython\u89e3\u91ca\u5668\u4e2d\u53ea\u6709\u4e00\u4e2aNone<\/code>\u5b9e\u4f8b\u3002\u56e0\u6b64\uff0c\u68c0\u67e5\u4e00\u4e2a\u53d8\u91cf\u662f\u5426\u4e3aNone<\/code>\u65f6\uff0c\u4f7f\u7528\u7684\u662fis<\/code>\u64cd\u4f5c\u7b26\u800c\u4e0d\u662f==<\/code>\u3002\u4f8b\u5982\uff1a<\/p>\n<\/p>\n
if my_variable is None:<\/p>\n
    print("my_variable is None")<\/p>\n
<\/code><\/pre>\n<\/p>\n
2\u3001\u5e03\u5c14\u4e0a\u4e0b\u6587\u4e2d\u7684None<\/code><\/h4>\n<\/p>\n
\u5728\u5e03\u5c14\u4e0a\u4e0b\u6587\u4e2d\uff0cNone<\/code>\u88ab\u89e3\u91ca\u4e3aFalse<\/code>\u3002\u8fd9\u610f\u5473\u7740\u5728\u6761\u4ef6\u8bed\u53e5\u4e2d\u53ef\u4ee5\u76f4\u63a5\u4f7f\u7528None<\/code>\u8fdb\u884c\u5224\u65ad\u3002\u4f8b\u5982\uff1a<\/p>\n<\/p>\n
if not my_variable:<\/p>\n
    print("my_variable is None or False")<\/p>\n
<\/code><\/pre>\n<\/p>\n
\u4e09\u3001\u4e0e\u5176\u4ed6\u7a7a\u503c\u7684\u6bd4\u8f83<\/h3>\n<\/p>\n
1\u3001\u7a7a\u5b57\u7b26\u4e32\u3001\u7a7a\u5217\u8868\u3001\u7a7a\u5b57\u5178<\/h4>\n<\/p>\n
\u5728Python\u4e2d\uff0c\u9664\u4e86None<\/code>\u4e4b\u5916\uff0c\u8fd8\u6709\u5176\u4ed6\u8868\u793a\u201c\u7a7a\u201d\u7684\u503c\uff0c\u4f8b\u5982\u7a7a\u5b57\u7b26\u4e32""<\/code>\u3001\u7a7a\u5217\u8868[]<\/code>\u548c\u7a7a\u5b57\u5178{}<\/code>\u3002\u8fd9\u4e9b\u503c\u5728\u5e03\u5c14\u4e0a\u4e0b\u6587\u4e2d\u4e5f\u88ab\u89e3\u91ca\u4e3aFalse<\/code>\u3002\u4f8b\u5982\uff1a<\/p>\n<\/p>\n
empty_string = ""<\/p>\n
empty_list = []<\/p>\n
empty_dict = {}<\/p>\n
if not empty_string:<\/p>\n
    print("empty_string is empty")<\/p>\n
if not empty_list:<\/p>\n
    print("empty_list is empty")<\/p>\n
if not empty_dict:<\/p>\n
    print("empty_dict is empty")<\/p>\n
<\/code><\/pre>\n<\/p>\n
2\u3001\u4e0eNone<\/code>\u7684\u533a\u522b<\/h4>\n<\/p>\n
\u5c3d\u7ba1\u8fd9\u4e9b\u7a7a\u503c\u5728\u5e03\u5c14\u4e0a\u4e0b\u6587\u4e2d\u88ab\u89e3\u91ca\u4e3aFalse<\/code>\uff0c\u4f46\u5b83\u4eec\u4e0eNone<\/code>\u662f\u4e0d\u540c\u7684\u3002None<\/code>\u8868\u793a\u7f3a\u5931\u6216\u672a\u8d4b\u503c\uff0c\u800c\u7a7a\u5b57\u7b26\u4e32\u3001\u7a7a\u5217\u8868\u548c\u7a7a\u5b57\u5178\u5219\u8868\u793a\u8fd9\u4e9b\u6570\u636e\u7c7b\u578b\u7684\u5b9e\u4f8b\u6ca1\u6709\u5305\u542b\u4efb\u4f55\u5143\u7d20\u3002\u4f8b\u5982\uff1a<\/p>\n<\/p>\n
my_variable = None<\/p>\n
empty_list = []<\/p>\n
print(my_variable is None)  # True<\/p>\n
print(empty_list is None)   # False<\/p>\n
<\/code><\/pre>\n<\/p>\n
\u56db\u3001\u5728\u6570\u636e\u5904\u7406\u4e2d\u4f7f\u7528None<\/code><\/h3>\n<\/p>\n
1\u3001\u5904\u7406\u7f3a\u5931\u6570\u636e<\/h4>\n<\/p>\n
\u5728\u6570\u636e\u5904\u7406\u4e2d\uff0cNone<\/code>\u901a\u5e38\u7528\u4e8e\u8868\u793a\u7f3a\u5931\u7684\u6570\u636e\u3002\u4f8b\u5982\uff0c\u5728\u8bfb\u53d6CSV\u6587\u4ef6\u65f6\uff0c\u5982\u679c\u67d0\u4e2a\u5b57\u6bb5\u6ca1\u6709\u503c\uff0c\u53ef\u4ee5\u4f7f\u7528None<\/code>\u6765\u8868\u793a\u7f3a\u5931\u503c\uff1a<\/p>\n<\/p>\n
import csv<\/p>\n
with open('data.csv') as csvfile:<\/p>\n
    reader = csv.DictReader(csvfile)<\/p>\n
    for row in reader:<\/p>\n
        if row['age'] == '':<\/p>\n
            row['age'] = None<\/p>\n
<\/code><\/pre>\n<\/p>\n
\u8fd9\u6837\u53ef\u4ee5\u65b9\u4fbf\u5730\u5bf9\u7f3a\u5931\u6570\u636e\u8fdb\u884c\u5904\u7406\u3002<\/p>\n<\/p>\n
2\u3001\u4e0epandas\u5e93\u7684\u7ed3\u5408\u4f7f\u7528<\/h4>\n<\/p>\n
\u5728\u4f7f\u7528pandas\u5e93\u5904\u7406\u6570\u636e\u65f6\uff0c\u7f3a\u5931\u503c\u901a\u5e38\u7528NaN<\/code>\uff08Not a Number\uff09\u6765\u8868\u793a\uff0c\u4f46None<\/code>\u4e5f\u53ef\u4ee5\u7528\u6765\u8868\u793a\u7f3a\u5931\u503c\u3002pandas\u5e93\u4e2d\u7684isnull()<\/code>\u548cnotnull()<\/code>\u51fd\u6570\u53ef\u4ee5\u7528\u6765\u68c0\u67e5\u7f3a\u5931\u503c\uff1a<\/p>\n<\/p>\n
import pandas as pd<\/p>\n
data = {'name': ['Alice', 'Bob', 'Charlie'], 'age': [25, None, 30]}<\/p>\n
df = pd.DataFrame(data)<\/p>\n
print(df)<\/p>\n
print(df.isnull())<\/p>\n
print(df.notnull())<\/p>\n
<\/code><\/pre>\n<\/p>\n
\u5728\u8fd9\u79cd\u60c5\u51b5\u4e0b\uff0cpandas\u4f1a\u81ea\u52a8\u5c06None<\/code>\u8f6c\u6362\u4e3aNaN<\/code>\uff0c\u5e76\u4e14isnull()<\/code>\u51fd\u6570\u53ef\u4ee5\u7528\u6765\u68c0\u67e5\u7f3a\u5931\u503c\u3002<\/p>\n<\/p>\n
\u4e94\u3001\u5904\u7406None<\/code>\u7684\u6ce8\u610f\u4e8b\u9879<\/h3>\n<\/p>\n
1\u3001\u907f\u514dNone<\/code>\u7684\u7c7b\u578b\u9519\u8bef<\/h4>\n<\/p>\n
\u5728\u5904\u7406None<\/code>\u65f6\uff0c\u9700\u8981\u6ce8\u610f\u907f\u514d\u7c7b\u578b\u9519\u8bef\u3002\u4f8b\u5982\uff0c\u8bd5\u56fe\u5bf9None<\/code>\u8fdb\u884c\u7b97\u672f\u8fd0\u7b97\u4f1a\u5bfc\u81f4\u9519\u8bef\uff1a<\/p>\n<\/p>\n
my_variable = None<\/p>\n
print(my_variable + 1)  # TypeError: unsupported operand type(s) for +: 'NoneType' and 'int'<\/p>\n
<\/code><\/pre>\n<\/p>\n
\u56e0\u6b64\uff0c\u5728\u5bf9\u53d8\u91cf\u8fdb\u884c\u64cd\u4f5c\u4e4b\u524d\uff0c\u5e94\u8be5\u68c0\u67e5\u53d8\u91cf\u662f\u5426\u4e3aNone<\/code>\u3002<\/p>\n<\/p>\n
2\u3001\u4f7f\u7528None<\/code>\u7684\u5b89\u5168\u6027\u68c0\u67e5<\/h4>\n<\/p>\n
\u5728\u7f16\u5199\u4ee3\u7801\u65f6\uff0c\u53ef\u4ee5\u4f7f\u7528is<\/code>\u64cd\u4f5c\u7b26\u68c0\u67e5\u53d8\u91cf\u662f\u5426\u4e3aNone<\/code>\uff0c\u4ece\u800c\u786e\u4fdd\u4ee3\u7801\u7684\u5b89\u5168\u6027\u3002\u4f8b\u5982\uff1a<\/p>\n<\/p>\n
def SAFe<\/a>_division(x, y):<\/p>\n
    if y is None or y == 0:<\/p>\n
        return None<\/p>\n
    return x \/ y<\/p>\n
<\/code><\/pre>\n<\/p>\n
\u8fd9\u6837\u53ef\u4ee5\u907f\u514d\u9664\u4ee5None<\/code>\u6216\u96f6\u7684\u9519\u8bef\u3002<\/p>\n<\/p>\n
\u516d\u3001\u603b\u7ed3<\/h3>\n<\/p>\n
\u5728Python\u8bed\u8a00\u4e2d\uff0c\u7a7a\u503c\u901a\u5e38\u7528None<\/code>\u6765\u8868\u793a\u3002None<\/code>\u662f\u4e00\u4e2a\u7279\u6b8a\u7684\u5e38\u91cf\uff0c\u7528\u4e8e\u8868\u793a\u7a7a\u503c\u3001\u672a\u8d4b\u503c\u3001\u7f3a\u5931\u503c\u548c\u9ed8\u8ba4\u503c\u3002None<\/code>\u5728\u5168\u5c40\u8303\u56f4\u5185\u552f\u4e00\u5b58\u5728\uff0c\u5e76\u4e14\u5728\u5e03\u5c14\u4e0a\u4e0b\u6587\u4e2d\u88ab\u89e3\u91ca\u4e3aFalse<\/code>\u3002\u5728\u5904\u7406\u6570\u636e\u65f6\uff0cNone<\/code>\u901a\u5e38\u7528\u4e8e\u8868\u793a\u7f3a\u5931\u6216\u672a\u8d4b\u503c\u7684\u72b6\u6001\u3002\u4f7f\u7528None<\/code>\u65f6\uff0c\u9700\u8981\u6ce8\u610f\u907f\u514d\u7c7b\u578b\u9519\u8bef\uff0c\u5e76\u4e14\u53ef\u4ee5\u4f7f\u7528is<\/code>\u64cd\u4f5c\u7b26\u68c0\u67e5\u53d8\u91cf\u662f\u5426\u4e3aNone<\/code>\u3002\u901a\u8fc7\u5408\u7406\u5730\u4f7f\u7528None<\/code>\uff0c\u53ef\u4ee5\u7f16\u5199\u51fa\u66f4\u52a0\u5065\u58ee\u548c\u5b89\u5168\u7684\u4ee3\u7801\u3002<\/p>\n<\/p>\n
\u76f8\u5173\u95ee\u7b54FAQs\uff1a<\/strong><\/h2>\n
 \u5728Python\u4e2d\uff0c\u5982\u4f55\u5224\u65ad\u4e00\u4e2a\u53d8\u91cf\u662f\u5426\u4e3a\u7a7a\u503c\uff1f<\/strong>
\u5728Python\u4e2d\uff0c\u53ef\u4ee5\u4f7f\u7528if not variable:<\/code>\u6765\u5224\u65ad\u4e00\u4e2a\u53d8\u91cf\u662f\u5426\u4e3a\u7a7a\u503c\u3002\u7a7a\u503c\u5728Python\u4e2d\u901a\u5e38\u4f7f\u7528None<\/code>\u8868\u793a\uff0c\u4f46\u5176\u4ed6\u7a7a\u7684\u96c6\u5408\u7c7b\u578b\uff08\u5982\u7a7a\u5b57\u7b26\u4e32""<\/code>\u3001\u7a7a\u5217\u8868[]<\/code>\u3001\u7a7a\u5143\u7ec4()<\/code>\u548c\u7a7a\u5b57\u5178{}<\/code>\uff09\u4e5f\u88ab\u89c6\u4e3a\u5047\u503c\u3002\u901a\u8fc7\u8fd9\u79cd\u65b9\u6cd5\uff0c\u53ef\u4ee5\u6709\u6548\u5730\u68c0\u67e5\u53d8\u91cf\u662f\u5426\u4e3a\u201c\u7a7a\u201d\u3002<\/p>\n
\u7a7a\u503c\u5728Python\u4e2d\u6709\u54ea\u4e9b\u5e38\u89c1\u7684\u5e94\u7528\u573a\u666f\uff1f<\/strong>
\u7a7a\u503c\u5728\u7f16\u7a0b\u4e2d\u5e38\u7528\u4e8e\u8868\u793a\u7f3a\u5931\u7684\u6570\u636e\u6216\u5c1a\u672a\u88ab\u8d4b\u503c\u7684\u72b6\u6001\u3002\u4f8b\u5982\uff0c\u5728\u6570\u636e\u5e93\u64cd\u4f5c\u4e2d\uff0c\u5982\u679c\u67d0\u4e2a\u5b57\u6bb5\u6ca1\u6709\u503c\uff0c\u901a\u5e38\u4f1a\u88ab\u8bbe\u7f6e\u4e3aNone<\/code>\u3002\u5728\u51fd\u6570\u7684\u53c2\u6570\u4e2d\uff0c\u4e5f\u53ef\u4ee5\u4f7f\u7528\u7a7a\u503c\u6765\u8868\u793a\u53ef\u9009\u53c2\u6570\uff0c\u4ece\u800c\u63d0\u9ad8\u51fd\u6570\u7684\u7075\u6d3b\u6027\u3002<\/p>\n
\u5982\u4f55\u5728Python\u4e2d\u5904\u7406\u7a7a\u503c\u4ee5\u907f\u514d\u7a0b\u5e8f\u9519\u8bef\uff1f<\/strong>
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