Python常见的错误汇总

Python常见的错误汇总

 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

错误：

TypeError: 'NoneType' object is not callable

【错误分析】我是在别的文件中写了一个函数，然后在python console调用使用该函数，出现了上述错误。原因是因为没有对别的文件中函数进行编译，只要打开该调用函数的文件，然后点击运行，之后再在python console中调用使用该函数就不会报错。

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

错误:

【错误分析】第二个参数必须为类，否则会报TypeError，所以正确的应该是这样的:

但如果第二个参数是类型对象，则不会报上面的错误，是允许的，比如说:

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

错误:

【错误分析】这个涉及到调用顺序问题，即解析方法的MRO调用顺序，在Python2.7版本之后，这样调用会报错，

必须是子类先放前面，然后才是父类.如下所示，方不会报错.

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

错误:

【错误分析】foo()未带参数self,也未带cls参数,属于类的静态方法，类的静态方法调用，实例不能直接调用，需要再声明一个静态方法

或者通过@staticmethod来调用

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

错误:

【错误分析】__dict__是实例的特殊属性，但在内建属性中，不存在__dict__属性，一般的情况是:

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

错误:

【错误分析】如果定义了构造器，它不应当返回任何对象，因为实例对象是自动在实例化调用后返回的。相应地，__init__()就不应当返回任何对象(应当为None);否则就可能出现冲突，因为只能返回实例。试着返回非None的任何其他对象都会导致TypeError异常

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

错误:

 

1 >>> def f(x, y):  
2     print x, y  
3 >>> t = ('a', 'b')  
4 >>> f(t)  
5   
6 Traceback (most recent call last):  
7   File "<pyshell#65>", line 1, in <module>  
8     f(t)  
9 TypeError: f() takes exactly 2 arguments (1 given)

 

 

 

【错误分析】不要误以为元组里有两个参数，将元组传进去就可以了，实际上元祖作为一个整体只是一个参数，

实际需要两个参数，所以报错。必需再传一个参数方可.

>>> f(t, 'var2')  
('a', 'b') var2  

更常用的用法: 在前面加*,代表引用元组 

>>> f(*t)  
'a', 'b'  

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 

错误:

 

1 >>> def func(y=2, x):  
2     return x + y  
3 SyntaxError: non-default argument follows default argument 

 

 

 

【错误分析】在C++,Python中默认参数从左往右防止，而不是相反。这可能跟参数进栈顺序有关。

1 >>> def func(x, y=2):  
2     return x + y  
3 >>> func(1)  
4 3 

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

错误:

 

1 >>> D1 = {'x':1, 'y':2}  
2 >>> D1['x']  
3 1  
4 >>> D1['z']  
5   
6 Traceback (most recent call last):  
7   File "<pyshell#185>", line 1, in <module>  
8     D1['z']  
9 KeyError: 'z' 

 

【错误分析】这是Python中字典键错误的提示，如果想让程序继续运行，可以用字典中的get方法，如果键存在，则获取该键对应的值，不存在的，返回None,也可打印提示信息.

>>> D1.get('z', 'Key Not Exist!')  
'Key Not Exist!' 

 

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错误:

>>> from math import sqrt  
>>> exec "sqrt = 1"  
>>> sqrt(4)  
  
Traceback (most recent call last):  
  File "<pyshell#22>", line 1, in <module>  
    sqrt(4)  
TypeError: 'int' object is not callable  

【错误分析】exec语句最有用的地方在于动态地创建代码字符串，但里面存在的潜在的风险，它会执行其他地方的字符串，在CGI中更是如此！比如例子中的sqrt = 1，从而改变了当前的命名空间，从math模块中导入的sqrt不再和函数名绑定而是成为了一个整数。要避免这种情况，可以通过增加in <scope>，其中<scope>就是起到放置代码字符串命名空间的字典。

1 >>> from math import sqrt  
2 >>> scope = {}  
3 >>> exec "sqrt = 1" in scope  
4 >>> sqrt(4)  
5 2.0 

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

错误:

>>> seq = [1, 2, 3, 4]  
>>> sep = '+'  
>>> sep.join(seq)  
  
Traceback (most recent call last):  
  File "<pyshell#25>", line 1, in <module>  
    sep.join(seq)  
TypeError: sequence item 0: expected string, int found  

【错误分析】join是split的逆方法，是非常重要的字符串方法，但不能用来连接整数型列表，所以需要改成:

1 >>> seq = ['1', '2', '3', '4']  
2 >>> sep = '+'  
3 >>> sep.join(seq)  
4 '1+2+3+4' 

 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

错误:

 

1 >>> print r'C:\Program Files\foo\bar\'  
2 SyntaxError: EOL while scanning string literal  

 

【错误分析】Python中原始字符串以r开头，里面可以放置任意原始字符，包括\，包含在字符中的\不做转义。

但是，不能放在末尾！也就是说，最后一个字符不能是\，如果真 需要的话，可以这样写:

>>> print r'C:\Program Files\foo\bar' "\\"  
C:\Program Files\foo\bar\  
>>> print r'C:\Program Files\foo\bar' + "\\"  
C:\Program Files\foo\bar\   

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 

代码:

bad = 'bad'  
  
try:  
    raise bad  
except bad:  
    print 'Got Bad!' 

错误:

>>>   
  
Traceback (most recent call last):  
  File "D:\Learn\Python\Learn.py", line 4, in <module>  
    raise bad  
TypeError: exceptions must be old-style classes or derived from BaseException, not str 

【错误分析】因所用的Python版本2.7,比较高的版本，raise触发的异常，只能是自定义类异常，而不能是字符串。所以会报错，字符串改为自定义类，就可以了。

class Bad(Exception):  
    pass  
  
def raiseException():  
    raise Bad()  
  
try:  
    raiseException()  
except Bad:  
    print 'Got Bad!' 

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

 错误：

class Super:  
    def method(self):  
        print "Super's method"  
  
class Sub(Super):  
    def method(self):  
        print "Sub's method"  
        Super.method()  
        print "Over..."  
  
S = Sub()  
S.method() 

执行上面一段代码，错误如下:

>>>   
Sub's method  
  
Traceback (most recent call last):  
  File "D:\Learn\Python\test.py", line 12, in <module>  
    S.method()  
  File "D:\Learn\Python\test.py", line 8, in method  
    Super.method()  
TypeError: unbound method method() must be called with Super instance as first argument (got nothing instead)  

【错误分析】Python中调用类的方法，必须与实例绑定，或者调用自身.

ClassName.method(x, 'Parm')

ClassName.method(self)

所以上面代码，要调用Super类的话，只需要加个self参数即可。

class Super:  
    def method(self):  
        print "Super's method"  
  
class Sub(Super):  
    def method(self):  
        print "Sub's method"  
        Super.method(self)  
        print "Over..."  
  
S = Sub()  
S.method()  
  
  
#输出结果  
>>>   
Sub's method  
Super's method  
Over... 

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

错误：

>>> reload(sys)  
Traceback (most recent call last):  
  File "<stdin>", line 1, in <module>  
NameError: name 'sys' is not defined  

【错误分析】reload期望得到的是对象，所以该模块必须成功导入。在没导入模块前，不能重载.

>>> import sys  
>>> reload(sys)  
<module 'sys' (built-in)>  

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

 错误 

>>> def f(x, y, z):  
    return x + y + z  
  
>>> args = (1,2,3)  
>>> print f(args)  
  
Traceback (most recent call last):  
  File "<pyshell#6>", line 1, in <module>  
    print f(args)  
TypeError: f() takes exactly 3 arguments (1 given)  

【错误分析】args是一个元组，如果是f(args)，那么元组是作为一个整体作为一个参数，

*args，才是将元组中的每个元素作为参数

>>> f(*args)  
6 

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

  错误：

>>> def f(a,b,c,d):  
...   print a,b,c,d  
...  
>>> args = (1,2,3,4)  
>>> f(**args)  
Traceback (most recent call last):  
  File "<stdin>", line 1, in <module>  
TypeError: f() argument after ** must be a mapping, not tuple 

【错误分析】错误原因**匹配并收集在字典中所有包含位置的参数，但传递进去的却是个元祖。

所以修改传递参数如下:

>>> args = {'a':1,'b':2,'c':3}  
>>> args['d'] = 4  
>>> f(**args)  
1 2 3 4 

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

【错误分析】在函数hider()内使用了内置变量open，但根据Python作用域规则LEGB的优先级:

先是查找本地变量==》模块内的其他函数==》全局变量==》内置变量，查到了即停止查找。

所以open在这里只是个字符串，不能作为打开文件来使用，所以报错，更改变量名即可。

可以导入__builtin__模块看到所有内置变量：异常错误、和内置方法

 import __builtin__
>>> dir(__builtin__)
['ArithmeticError', 'AssertionError', 'AttributeError',...
  ........................................zip,filter,map]

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

 错误：

In [105]: T1 = (1)  
In [106]: T2 = (2,3)  
In [107]: T1 + T2  
---------------------------------------------------------------------------  
TypeError                                 Traceback (most recent call last)  
<ipython-input-107-b105c7b32d90> in <module>()  
----> 1 T1 + T2;  
  
TypeError: unsupported operand type(s) for +: 'int' and 'tuple'  

【错误分析】(1)的类型是整数，所以不能与另一个元祖做合并操作，如果只有一个元素的元祖，应该用(1,)来表示

In [108]: type(T1)  
Out[108]: int  
  
In [109]: T1 = (1,)  
In [110]: T2 = (2,3)  
In [111]: T1 + T2  
Out[111]: (1, 2, 3) 

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

 错误：

>>> hash(1,(2,[3,4]))  
  
Traceback (most recent call last):  
  File "<pyshell#95>", line 1, in <module>  
    hash((1,2,(2,[3,4])))  
TypeError: unhashable type: 'list'  

【错误分析】字典中的键必须是不可变对象，如(整数，浮点数，字符串，元组).

可用hash()判断某个对象是否可哈希

>>> hash('string')  
-1542666171

但列表中元素是可变对象，所以是不可哈希的，所以会报上面的错误.

如果要用列表作为字典中的键，最简单的办法是:

>>> D = {}  
>>> D[tuple([3,4])] = 5  
>>> D  
{(3, 4): 5}  

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

错误：

>>> L = [2,1,4,3]  
>>> L.reverse().sort()  
Traceback (most recent call last):  
  File "<stdin>", line 1, in <module>  
AttributeError: 'NoneType' object has no attribute 'sort'  
>>> L  
[3, 4, 1, 2]  

【错误分析】列表属于可变对象,其append(),sort(),reverse()会在原处修改对象，不会有返回值，

或者说返回值为空，所以要实现反转并排序，不能并行操作，要分开来写。

>>> L = [2,1,4,3]  
>>> L.reverse()  
>>> L.sort()  
>>> L  
[1, 2, 3, 4] 

或者用下面的方法实现:

In [103]: sorted(reversed([2,1,4,3]))  
Out[103]: [1, 2, 3, 4]  

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

 错误：

>>> class = 78  
SyntaxError: invalid syntax  

【错误分析】class是Python保留字，Python保留字不能做变量名，可以用Class，或klass
同样，保留字不能作为模块名来导入，比如说，有个and.py，但不能将其作为模块导入

>>> import and  
SyntaxError: invalid syntax  

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

错误：

>>> f = open('D:\new\text.data','r')  
Traceback (most recent call last):  
  File "<stdin>", line 1, in <module>  
IOError: [Errno 22] invalid mode ('r') or filename: 'D:\new\text.data'  
>>> f = open(r'D:\new\text.data','r')  
>>> f.read()  
'Very\ngood\naaaaa'  

【错误分析】\n默认为换行，\t默认为TAB键.

所以在D:\目录下找不到ew目录下的ext.data文件，将其改为raw方式输入即可。

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

错误：

try:  
    print 1 / 0  
      
except ZeroDivisionError:  
    print 'integer division or modulo by zero'  
      
finally:  
    print 'Done'  
  
else:    
    print 'Continue Handle other part'  
报错如下:  
D:\>python Learn.py  
  File "Learn.py", line 11  
    else:  
       ^  
SyntaxError: invalid syntax  

【错误分析】错误原因，else, finally执行位置;正确的程序应该如下:

try:  
    print 1 / 0  
      
except ZeroDivisionError:  
    print 'integer division or modulo by zero'  
  
  
else:    
    print 'Continue Handle other part'  
      
finally:  
    print 'Done' 

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

错误： 

>>> [x,y for x in range(2) for y in range(3)]  
  File "<stdin>", line 1  
    [x,y for x in range(2) for y in range(3)]  
           ^  
SyntaxError: invalid syntax  

【错误分析】错误原因，列表解析中，x,y必须以数组的方式列出(x,y)

>>> [(x,y) for x in range(2) for y in range(3)]  
[(0, 0), (0, 1), (0, 2), (1, 0), (1, 1), (1, 2)]  

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

class JustCounter:  
    __secretCount = 0  
  
    def count(self):  
        self.__secretCount += 1  
        print 'secretCount is:', self.__secretCount  
  
count1 = JustCounter()  
  
count1.count()  
count1.count()  
  
count1.__secretCount  

报错如下:

>>>   
secretCount is: 1  
secretCount is: 2  
  
  
Traceback (most recent call last):  
  File "D:\Learn\Python\Learn.py", line 13, in <module>  
    count1.__secretCount  
AttributeError: JustCounter instance has no attribute '__secretCount'  

【错误分析】双下划线的类属性__secretCount不可访问，所以会报无此属性的错误. 

解决办法如下:

# 1. 可以通过其内部成员方法访问  
# 2. 也可以通过访问  
ClassName._ClassName__Attr  
#或   
ClassInstance._ClassName__Attr  
#来访问，比如：  
print count1._JustCounter__secretCount  
print JustCounter._JustCounter__secretCount  

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

>>> t = (1,2)  
>>> t.append(3)  
Traceback (most recent call last):  
  File "<stdin>", line 1, in <module>  
AttributeError: 'tuple' object has no attribute 'append'  
>>> t.remove(2)  
Traceback (most recent call last):  
  File "<stdin>", line 1, in <module>  
AttributeError: 'tuple' object has no attribute 'remove'  
>>> t.pop()  
Traceback (most recent call last):  
  File "<stdin>", line 1, in <module>  
AttributeError: 'tuple' object has no attribute 'pop'  

【错误分析】属性错误,归根到底在于元组是不可变类型，所以没有这几种方法.
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

>>> t = ()  
>>> t[0]  
Traceback (most recent call last):  
  File "<stdin>", line 1, in <module>  
IndexError: tuple index out of range  
>>> l = []  
>>> l[0]  
Traceback (most recent call last):  
  File "<stdin>", line 1, in <module>  
IndexError: list index out of range

【错误分析】空元组和空列表，没有索引为0的项
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

>>> if X>Y:  
...  X,Y = 3,4  
...   print X,Y  
  File "<stdin>", line 3  
    print X,Y  
    ^  
IndentationError: unexpected indent  
  
  
>>>   t = (1,2,3,4)  
  File "<stdin>", line 1  
    t = (1,2,3,4)  
    ^  
IndentationError: unexpected indent

【错误分析】一般出在代码缩进的问题
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

>>> f = file('1.txt')  
>>> f.readline()  
'AAAAA\n'  
>>> f.readline()  
'BBBBB\n'  
>>> f.next()  
'CCCCC\n'

【错误分析】如果文件里面没有行了会报这种异常

>>> f.next() #  
Traceback (most recent call last):  
  File "<stdin>", line 1, in <module>  
StopIteration  

有可迭代的对象的next方法,会前进到下一个结果,而在一系列结果的末尾时,会引发StopIteration的异常.

next()方法属于Python的魔法方法，这种方法的效果就是:逐行读取文本文件的最佳方式就是根本不要去读取。

取而代之的用for循环去遍历文件，自动调用next()去调用每一行，且不会报错

for line in open('test.txt','r'):  
    print line 

 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

>>> string = 'SPAM'  
>>> a,b,c = string  
Traceback (most recent call last):  
  File "<stdin>", line 1, in <module>  
ValueError: too many values to unpack  

【错误分析】接受的变量少了，应该是

>>> a,b,c,d = string  
>>> a,d  
('S', 'M')  
#除非用切片的方式  
>>> a,b,c = string[0],string[1],string[2:]  
>>> a,b,c  
('S', 'P', 'AM')  
或者  
>>> a,b,c = list(string[:2]) + [string[2:]]  
>>> a,b,c  
('S', 'P', 'AM')  
或者  
>>> (a,b),c = string[:2],string[2:]  
>>> a,b,c  
('S', 'P', 'AM')  
或者  
>>> ((a,b),c) = ('SP','AM')  
>>> a,b,c  
('S', 'P', 'AM')  
  
简单点就是:  
>>> a,b = string[:2]  
>>> c   = string[2:]  
>>> a,b,c  
('S', 'P', 'AM') 

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

>>> mydic={'a':1,'b':2}  
>>> mydic['a']  
1  
>>> mydic['c']  
Traceback (most recent call last):  
  File "<stdin>", line 1, in ?  
KeyError: 'c'  

【错误分析】当映射到字典中的键不存在时候，就会触发此类异常, 或者可以，这样测试

>>> 'a' in mydic.keys()  
True  
>>> 'c' in mydic.keys()              #用in做成员归属测试  
False  
>>> D.get('c','"c" is not exist!')   #用get或获取键，如不存在，会打印后面给出的错误信息  
'"c" is not exist!'  

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

File "study.py", line 3  
  return None  
  ^  
dentationError: unexpected indent  

【错误分析】一般是代码缩进问题，TAB键或空格键不一致导致

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

>>>def A():  
return A()  
>>>A() #无限循环，等消耗掉所有内存资源后，报最大递归深度的错误    
File "<pyshell#2>", line 2, in A return A()RuntimeError: maximum recursion depth exceeded  
class Bird:  
    def __init__(self):  
        self.hungry = True  
    def eat(self):  
        if self.hungry:  
            print "Ahaha..."  
            self.hungry = False  
        else:  
            print "No, Thanks!"  
该类定义鸟的基本功能吃，吃饱了就不再吃  
输出结果:  
>>> b = Bird()  
>>> b.eat()  
Ahaha...  
>>> b.eat()  
No, Thanks!  
下面一个子类SingBird,  
class SingBird(Bird):  
    def __init__(self):  
        self.sound = 'squawk'  
    def sing(self):  
        print self.sound  
输出结果:  
>>> s = SingBird()  
>>> s.sing()  
squawk  
SingBird是Bird的子类，但如果调用Bird类的eat()方法时,  
>>> s.eat()  
Traceback (most recent call last):  
  File "<pyshell#5>", line 1, in <module>  
    s.eat()  
  File "D:\Learn\Python\Person.py", line 42, in eat  
    if self.hungry:  
AttributeError: SingBird instance has no attribute 'hungry' 

【错误分析】代码错误很清晰,SingBird中初始化代码被重写，但没有任何初始化hungry的代码

class SingBird(Bird):  
    def __init__(self):  
        self.sound = 'squawk'  
        self.hungry = Ture #加这么一句  
    def sing(self):  
        print self.sound  

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

class Bird:  
    def __init__(self):  
        self.hungry = True  
    def eat(self):  
        if self.hungry:  
            print "Ahaha..."  
            self.hungry = False  
        else:  
            print "No, Thanks!"  
  
class SingBird(Bird):  
    def __init__(self):  
        super(SingBird,self).__init__()  
        self.sound = 'squawk'  
    def sing(self):  
        print self.sound  
>>> sb = SingBird()  
Traceback (most recent call last):  
  File "<pyshell#5>", line 1, in <module>  
    sb = SingBird()  
  File "D:\Learn\Python\Person.py", line 51, in __init__  
    super(SingBird,self).__init__()  
TypeError: must be type, not classobj  

【错误分析】在模块首行里面加上__metaclass__=type，具体还没搞清楚为什么要加

__metaclass__=type  
class Bird:  
    def __init__(self):  
        self.hungry = True  
    def eat(self):  
        if self.hungry:  
            print "Ahaha..."  
            self.hungry = False  
        else:  
            print "No, Thanks!"  
  
class SingBird(Bird):  
    def __init__(self):  
        super(SingBird,self).__init__()  
        self.sound = 'squawk'  
    def sing(self):  
        print self.sound  
>>> S = SingBird()  
>>> S.  
SyntaxError: invalid syntax  
>>> S.  
SyntaxError: invalid syntax  
>>> S.eat()  
Ahaha... 

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

【错误】

 

1 >>> T  
2 (1, 2, 3, 4)  
3 >>> T[0] = 22   
4 Traceback (most recent call last):  
5   File "<pyshell#129>", line 1, in <module>  
6     T[0] = 22  
7 TypeError: 'tuple' object does not support item assignment  

 

 

>>> T  
(1, 2, 3, 4)  
>>> T[0] = 22   
Traceback (most recent call last):  
  File "<pyshell#129>", line 1, in <module>  
    T[0] = 22  
TypeError: 'tuple' object does not support item assignment  

【错误分析】元组不可变，所以不可以更改;可以用切片或合并的方式达到目的.

>>> T = (1,2,3,4)  
>>> (22,) + T[1:]  
(22, 2, 3, 4)  

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

>>> X = 1;  
>>> Y = 2;  
>>> X + = Y  
  File "<stdin>", line 1  
    X + = Y  
        ^  
SyntaxError: invalid syntax  

【错误分析】增强行赋值不能分开来写，必须连着写比如说 +=, *=

>>> X += Y  
>>> X;Y  
3  
2

 参考：http://blog.csdn.net/jerry_1126/article/details/39395899