python - 如何在 try/except block 中公开变量？

Question

如何在 try/except block 中公开变量？

import urllib.request

try:
    url = "http://www.google.com"
    page = urllib.request.urlopen(url)
    text = page.read().decode('utf8')
except (ValueError, RuntimeError, TypeError, NameError):
    print("Unable to process your request dude!!")

print(text)

此代码返回错误

NameError: name 'text' is not defined

如何使变量文本在 try/except block 之外可用？

Answer 1

try 语句不会创建新范围，但如果调用 url lib.request.urlopen 则不会设置 text引发异常。您可能希望 else 子句中的 print(text) 行，以便仅在没有异常时执行。

try:
    url = "http://www.google.com"
    page = urllib.request.urlopen(url)
    text = page.read().decode('utf8')
except (ValueError, RuntimeError, TypeError, NameError):
    print("Unable to process your request dude!!")
else:
    print(text)

如果以后需要使用text，你真的需要考虑一下如果给page的赋值失败，你不能调用它的值应该是什么page.read()。你可以在 try 语句之前给它一个初始值:

text = 'something'
try:
    url = "http://www.google.com"
    page = urllib.request.urlopen(url)
    text = page.read().decode('utf8')
except (ValueError, RuntimeError, TypeError, NameError):
    print("Unable to process your request dude!!")

print(text)

或在 else 子句中:

try:
    url = "http://www.google.com"
    page = urllib.request.urlopen(url)
    text = page.read().decode('utf8')
except (ValueError, RuntimeError, TypeError, NameError):
    print("Unable to process your request dude!!")
else:
    text = 'something'

print(text)