Python的各种错误类型

当我们编写代码时，通常会出现拼写错误或其他常见错误。如果我们的代码无法运行，Python解释器将显示一条消息，其中包含有关问题发生位置和错误类型的反馈信息。它有时还会给我们提出可能修复的建议。了解编程语言中不同类型的错误会帮助我们快速调试代码，也使我们更擅长所做的工作。

让我们逐个查看最常见的错误类型。首先让我们打开Python交互式shell。进入计算机终端并输入“python”。Python交互式shell将打开。

SyntaxError语法错误

示例1:SyntaxError

asabeneh@Asabeneh:~$ python
Python 3.9.6 (default, Jun 28 2021, 15:26:21)
[Clang 11.0.0 (clang-1100.0.33.8)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> print 'hello world'
  File "<stdin>", line 1
    print 'hello world'
                      ^
SyntaxError: Missing parentheses in call to 'print'. Did you mean print('hello world')?
>>>

如您所见，我们因为忘记使用括号将字符串括起来而造成了语法错误，Python已经给出了解决方案。让我们来修复它。

asabeneh@Asabeneh:~$ python
Python 3.9.6 (default, Jun 28 2021, 15:26:21)
[Clang 11.0.0 (clang-1100.0.33.8)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> print 'hello world'
  File "<stdin>", line 1
    print 'hello world'
                      ^
SyntaxError: Missing parentheses in call to 'print'. Did you mean print('hello world')?
>>> print('hello world')
hello world
>>>

错误是一个SyntaxError。修复后我们的代码执行得非常顺利。让我们看看更多的错误类型。

NameError命名错误

示例1:NameError

asabeneh@Asabeneh:~$ python
Python 3.9.6 (default, Jun 28 2021, 15:26:21)
[Clang 11.0.0 (clang-1100.0.33.8)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> print(age)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'age' is not defined
>>>

从上面的消息中可以看出，名称年龄未定义。是的，我们确实没有定义一个年龄变量，但我们试图将其打印出来，就好像我们已经声明了它一样。 现在，让我们通过声明它并赋值来解决这个问题。

asabeneh@Asabeneh:~$ python
Python 3.9.6 (default, Jun 28 2021, 15:26:21)
[Clang 11.0.0 (clang-1100.0.33.8)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> print(age)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'age' is not defined
>>> age = 25
>>> print(age)
25
>>>

错误类型是NameError。我们通过定义变量名称调试了该错误。

IndexError索引错误

示例1:IndexError

asabeneh@Asabeneh:~$ python
Python 3.9.6 (default, Jun 28 2021, 15:26:21)
[Clang 11.0.0 (clang-1100.0.33.8)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> numbers = [1, 2, 3, 4, 5]
>>> numbers[5]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
IndexError: list index out of range
>>>

在上面的示例中，Python引发了IndexError，因为该列表仅具有从0到4的索引，因此超出了范围。

ModuleNotFoundError无法访问模块错误

示例1:ModuleNotFoundError

asabeneh@Asabeneh:~$ python
Python 3.9.6 (default, Jun 28 2021, 15:26:21)
[Clang 11.0.0 (clang-1100.0.33.8)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import maths
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ModuleNotFoundError: No module named 'maths'
>>>

在上面的例子中，我故意在math中添加了一个额外的s，导致出现了ModuleNotFoundError。让我们通过从math中移除额外的s来修复它。

asabeneh@Asabeneh:~$ python
Python 3.9.6 (default, Jun 28 2021, 15:26:21)
[Clang 11.0.0 (clang-1100.0.33.8)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import maths
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ModuleNotFoundError: No module named 'maths'
>>> import math
>>>

我们修复了它，那么让我们使用一些来自math模块的函数。

AttributeError属性错误

示例1:AttributeError

asabeneh@Asabeneh:~$ python
Python 3.9.6 (default, Jun 28 2021, 15:26:21)
[Clang 11.0.0 (clang-1100.0.33.8)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import maths
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ModuleNotFoundError: No module named 'maths'
>>> import math
>>> math.PI
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: module 'math' has no attribute 'PI'
>>>

您可以看到，我又犯了错！我尝试从数学模块调用PI函数，而不是pi。它引发了属性错误，这意味着该函数在模块中不存在。我们通过将PI更改为pi来修复它。

asabeneh@Asabeneh:~$ python
Python 3.9.6 (default, Jun 28 2021, 15:26:21)
[Clang 11.0.0 (clang-1100.0.33.8)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import maths
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ModuleNotFoundError: No module named 'maths'
>>> import math
>>> math.PI
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: module 'math' has no attribute 'PI'
>>> math.pi
3.141592653589793
>>>

现在，当我们从math模块调用pi时，我们得到了结果。

KeyError关键字错误

示例1:KeyError

asabeneh@Asabeneh:~$ python
Python 3.9.6 (default, Jun 28 2021, 15:26:21)
[Clang 11.0.0 (clang-1100.0.33.8)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> users = {'name':'Asab', 'age':250, 'country':'Finland'}
>>> users['name']
'Asab'
>>> users['county']
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
KeyError: 'county'
>>>

正如你所看到的，获取字典值所用的关键字存在一个拼写错误。所以，这是一个关键字错误，修复起来非常简单。让我们开始吧！

asabeneh@Asabeneh:~$ python
Python 3.9.6 (default, Jun 28 2021, 15:26:21)
[Clang 11.0.0 (clang-1100.0.33.8)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> user = {'name':'Asab', 'age':250, 'country':'Finland'}
>>> user['name']
'Asab'
>>> user['county']
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
KeyError: 'county'
>>> user['country']
'Finland'
>>>

我们已经除错了，我们的代码跑起来了，并且我们得到了值。

TypeError类型错误

示例1:TypeError

asabeneh@Asabeneh:~$ python
Python 3.9.6 (default, Jun 28 2021, 15:26:21)
[Clang 11.0.0 (clang-1100.0.33.8)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> 4 + '3'
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unsupported operand type(s) for +: 'int' and 'str'
>>>

在上面的例子中，会引发TypeError，因为我们不能将数字添加到字符串中。第一个解决方案是将字符串转换为int或float。另一个解决方案是将数字转换为字符串（结果将变为'43'）。让我们遵循第一个修复。

asabeneh@Asabeneh:~$ python
Python 3.9.6 (default, Jun 28 2021, 15:26:21)
[Clang 11.0.0 (clang-1100.0.33.8)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> 4 + '3'
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unsupported operand type(s) for +: 'int' and 'str'
>>> 4 + int('3')
7
>>> 4 + float('3')
7.0
>>>

错误已经被移除，我们得到了预期的结果。

ImportError导入错误

示例1:

asabeneh@Asabeneh:~$ python
Python 3.9.6 (default, Jun 28 2021, 15:26:21)
[Clang 11.0.0 (clang-1100.0.33.8)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from math import power
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: cannot import name 'power' from 'math'
>>>

数学模块中没有名为power的函数，它有不同的名称：pow。让我们来纠正它：

asabeneh@Asabeneh:~$ python
Python 3.9.6 (default, Jun 28 2021, 15:26:21)
[Clang 11.0.0 (clang-1100.0.33.8)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from math import power
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: cannot import name 'power' from 'math'
>>> from math import pow
>>> pow(2,3)
8.0
>>>

ValueError值错误

asabeneh@Asabeneh:~$ python
Python 3.9.6 (default, Jun 28 2021, 15:26:21)
[Clang 11.0.0 (clang-1100.0.33.8)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> int('12a')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: invalid literal for int() with base 10: '12a'
>>>

在此情况下，我们无法将给定的字符串更改为数字，因为其中含有字母“a”。

ZeroDivisionError除以0错误

asabeneh@Asabeneh:~$ python
Python 3.9.6 (default, Jun 28 2021, 15:26:21)
[Clang 11.0.0 (clang-1100.0.33.8)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> 1/0
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ZeroDivisionError: division by zero
>>>

我们不能用一个数字除以0。

我们已经涵盖了一些 Python 错误类型，如果你想查看更多关于它的内容，请查看有关 Python 错误类型的 Python 文档。如果你擅长阅读错误类型，那么你将能够快速解决错误并成为一名更好的程序员。