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自己编程中遇到的Python错误和解决方法汇总整理

  • 时间:2022-12-08 01:10 编辑: 来源: 阅读:
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摘要:自己编程中遇到的Python错误和解决方法汇总整理
开个贴,用于记录平时经常碰到的Python的错误同时对导致错误的原因进行分析,并持续更新,方便以后查询,学习。 知识在于积累嘛!微笑 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 错误:
[u]复制代码[/u] 代码如下:
>>> def f(x, y):      print x, y  >>> t = ('a', 'b')  >>> f(t)    Traceback (most recent call last):    File "<pyshell#65>", line 1, in <module>      f(t)  TypeError: f() takes exactly 2 arguments (1 given) 
【错误分析】不要误以为元祖里有两个参数,将元祖传进去就可以了,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.
[u]复制代码[/u] 代码如下:
>>> f(t, 'var2')  ('a', 'b') var2 
更常用的用法: 在前面加*,代表引用元祖
[u]复制代码[/u] 代码如下:
>>> f(*t)  'a', 'b' 
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 错误:
[u]复制代码[/u] 代码如下:
>>> def func(y=2, x):      return x + y  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。
[u]复制代码[/u] 代码如下:
>>> def func(x, y=2):      return x + y  >>> func(1)  3 
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 错误:
[u]复制代码[/u] 代码如下:
>>> D1 = {'x':1, 'y':2}  >>> D1['x']  1  >>> D1['z']    Traceback (most recent call last):    File "<pyshell#185>", line 1, in <module>      D1['z']  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.
[u]复制代码[/u] 代码如下:
>>> D1.get('z', 'Key Not Exist!')  'Key Not Exist!' 
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 错误:
[u]复制代码[/u] 代码如下:
>>> 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。
[u]复制代码[/u] 代码如下:
>>> from math import sqrt  >>> scope = {}  >>> exec "sqrt = 1" in scope  >>> sqrt(4)  2.0 
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 错误:
[u]复制代码[/u] 代码如下:
>>> 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:
[u]复制代码[/u] 代码如下:
>>> seq = ['1', '2', '3', '4']  >>> sep = '+'  >>> sep.join(seq)  '1+2+3+4' 
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 错误:
[u]复制代码[/u] 代码如下:
>>> print r'C:\Program Files\foo\bar\'  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:
[u]复制代码[/u] 代码如下:
>>> 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:
[u]复制代码[/u] 代码如下:
bad = 'bad'    try:      raise bad  except bad:      print 'Got Bad!' 
错误:
[u]复制代码[/u] 代码如下:
>>>     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。
[u]复制代码[/u] 代码如下:
class Bad(Exception):      pass    def raiseException():      raise Bad()    try:      raiseException()  except Bad:      print 'Got Bad!'   
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
[u]复制代码[/u] 代码如下:
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:
[u]复制代码[/u] 代码如下:
>>>   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.
[u]复制代码[/u] 代码如下:
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。
[u]复制代码[/u] 代码如下:
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... 
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
[u]复制代码[/u] 代码如下:
>>> 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.
[u]复制代码[/u] 代码如下:
>>> import sys  >>> reload(sys)  <module 'sys' (built-in)> 
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
[u]复制代码[/u] 代码如下:
>>> 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是一个元祖,如果是f(args),那么元祖是作为一个整体作为一个参数 *args,才是将元祖中的每个元素作为参数
[u]复制代码[/u] 代码如下:
>>> f(*args)  6 
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
[u]复制代码[/u] 代码如下:
>>> 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:
[u]复制代码[/u] 代码如下:
>>> args = {'a':1,'b':2,'c':3}  >>> args['d'] = 4  >>> f(**args)  1 2 3 4 
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ [img]http://files.jb51.net/file_images/article/201506/201563110845401.png?20155311853[/img] 【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
[u]复制代码[/u] 代码如下:
>>> import __builtin__ >>> dir(__builtin__) ['ArithmeticError', 'AssertionError', 'AttributeError',..   .........................................zip,filter,map]  
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
[u]复制代码[/u] 代码如下:
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
[u]复制代码[/u] 代码如下:
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) 
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
[u]复制代码[/u] 代码如下:
>>> 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,元祖). 可用hash()判断某个对象是否可哈希
[u]复制代码[/u] 代码如下:
>>> 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:
[u]复制代码[/u] 代码如下:
>>> D = {}  >>> D[tuple([3,4])] = 5  >>> D  {(3, 4): 5} 
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
[u]复制代码[/u] 代码如下:
>>> 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
[u]复制代码[/u] 代码如下:
>>> L = [2,1,4,3]  >>> L.reverse()  >>> L.sort()  >>> L  [1, 2, 3, 4] 
或者用下面的方法实现:
[u]复制代码[/u] 代码如下:
In [103]: sorted(reversed([2,1,4,3]))  Out[103]: [1, 2, 3, 4] 
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
[u]复制代码[/u] 代码如下:
>>> 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
[u]复制代码[/u] 代码如下:
>>> import and  SyntaxError: invalid syntax 
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
[u]复制代码[/u] 代码如下:
>>> 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。 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
[u]复制代码[/u] 代码如下:
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:
[u]复制代码[/u] 代码如下:
try:      print 1 / 0        except ZeroDivisionError:      print 'integer division or modulo by zero'      else:        print 'Continue Handle other part'        finally:      print 'Done' 
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
[u]复制代码[/u] 代码如下:
>>> [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)
[u]复制代码[/u] 代码如下:
>>> [(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:
[u]复制代码[/u] 代码如下:
>>>   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:
[u]复制代码[/u] 代码如下:
# 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  
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
[u]复制代码[/u] 代码如下:
>>> print x  Traceback (most recent call last):    File "<stdin>", line 1, in <module>  NameError: name 'x' is not defined  >>> x = 1  >>> print x  1 
【错误分析】Python不允许使用未赋值变量 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
[u]复制代码[/u] 代码如下:
>>> 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,归根到底在于元祖是不可变类型,所以没有这几种方法. +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
[u]复制代码[/u] 代码如下:
>>> 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】空元祖和空列表,没有索引为0的项 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
[u]复制代码[/u] 代码如下:
>>> 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 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
[u]复制代码[/u] 代码如下:
>>> 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
[u]复制代码[/u] 代码如下:
>>> 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
[u]复制代码[/u] 代码如下:
for line in open('test.txt','r'):      print line 
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
[u]复制代码[/u] 代码如下:
>>> 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
[u]复制代码[/u] 代码如下:
>>> 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') 
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
[u]复制代码[/u] 代码如下:
>>> 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
[u]复制代码[/u] 代码如下:
>>> '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!' 
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
[u]复制代码[/u] 代码如下:
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 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
[u]复制代码[/u] 代码如下:
>>>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: 
[u]复制代码[/u] 代码如下:
>>> b = Bird()  >>> b.eat()  Ahaha...  >>> b.eat()  No, Thanks! 
下面一个子类SingBird, 
[u]复制代码[/u] 代码如下:
class SingBird(Bird):      def __init__(self):          self.sound = 'squawk'      def sing(self):          print self.sound
   输出结果: 
[u]复制代码[/u] 代码如下:
>>> s = SingBird()  >>> s.sing()  squawk 
SingBird是Bird的子类,但如果调用Bird类的eat()方法时, 
[u]复制代码[/u] 代码如下:
>>> 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
[u]复制代码[/u] 代码如下:
class SingBird(Bird):      def __init__(self):          self.sound = 'squawk'          self.hungry = Ture #加这么一句      def sing(self):          print self.sound 
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
[u]复制代码[/u] 代码如下:
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
[u]复制代码[/u] 代码如下:
__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... 
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[u]复制代码[/u] 代码如下:
>>> 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】元祖不可变,所以不可以更改;可以用切片或合并的方式达到目的.
[u]复制代码[/u] 代码如下:
>>> T = (1,2,3,4)  >>> (22,) + T[1:]  (22, 2, 3, 4) 
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[u]复制代码[/u] 代码如下:
>>> 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 +=, *=
[u]复制代码[/u] 代码如下:
>>> X += Y  >>> X;Y  3  2 
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