如何在try/except块public中创建一个变量？

Question

如何在try/except块public中创建变量？

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__CODE__.

如何在try/except块之外使变量文本可用？

Answer 1

try语句不会创建新范围,但text如果调用url lib.request.urlopen引发异常,则不会设置.您可能希望print(text)在else子句中使用该行,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text需要使用,你真的需要考虑如果赋值page失败而你无法调用它的值应该是什么page.read().您可以在try声明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条款中:

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)

Answer 2

text只需在块外声明变量即可try except，

import urllib.request
text =None
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!!")
if text is not None:
    print(text)

Answer 3

正如之前回答的那样， usingtry except子句没有引入新的范围，因此如果没有发生异常，您应该在locals列表中看到您的变量，并且它应该可以在当前（在您的情况下为全局）范围内访问。

print(locals())

在模块范围内（您的情况） locals() == globals()