自己编程中遇到的Python错误和解决方法汇总整理

发表于 5年以前 | 总阅读数：581 次

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
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错误:

复制代码 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
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.

复制代码 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

复制代码 代码如下:

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

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
错误:

复制代码 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。

复制代码 代码如下:

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

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错误:

复制代码 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
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.

复制代码 代码如下:

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

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错误:

复制代码 代码如下:

from math import sqrt
exec "sqrt = 1"
sqrt(4)

Traceback (most recent call last):
File "<pyshell#22>", line 1, in
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 ，其中就是起到放置代码字符串命名空间的字典。

复制代码 代码如下:

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

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错误:

复制代码 代码如下:

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

Traceback (most recent call last):
File "<pyshell#25>", line 1, in
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:

复制代码 代码如下:

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

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错误:

复制代码 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:

复制代码 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\

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代码:

复制代码 代码如下:

bad = 'bad'

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

错误:

复制代码 代码如下:

Traceback (most recent call last):
File "D:\Learn\Python\Learn.py", line 4, in
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。

复制代码 代码如下:

class Bad(Exception):
pass

def raiseException():
raise Bad()

try:
raiseException()
except Bad:
print 'Got Bad!'

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

复制代码 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:

复制代码 代码如下:

Sub's method

Traceback (most recent call last):
File "D:\Learn\Python\test.py", line 12, in
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.

复制代码 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。

复制代码 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...

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

复制代码 代码如下:

reload(sys)
Traceback (most recent call last):
File "", line 1, in
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.

复制代码 代码如下:

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

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复制代码 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
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

复制代码 代码如下:

f(*args)
6

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

复制代码 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 "", line 1, in
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:

复制代码 代码如下:

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

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【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

复制代码 代码如下:

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

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复制代码 代码如下:

In [105]: T1 = (1)
In [106]: T2 = (2,3)
In [107]: T1 + T2
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)

in () \----> 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

复制代码 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)

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复制代码 代码如下:

hash(1,(2,[3,4]))

Traceback (most recent call last):
File "<pyshell#95>", line 1, in
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

复制代码 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:

复制代码 代码如下:

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

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复制代码 代码如下:

L = [2,1,4,3]
L.reverse().sort()
Traceback (most recent call last):
File "", line 1, in
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

复制代码 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:

复制代码 代码如下:

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

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复制代码 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

复制代码 代码如下:

import and
SyntaxError: invalid syntax

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复制代码 代码如下:

f = open('D:\new\text.data','r')
Traceback (most recent call last):
File "", line 1, in
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。
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

复制代码 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:

复制代码 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'

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

复制代码 代码如下:

[x,y for x in range(2) for y in range(3)]
File "", 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)

复制代码 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:

复制代码 代码如下:

secretCount is: 1
secretCount is: 2

Traceback (most recent call last):
File "D:\Learn\Python\Learn.py", line 13, in
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:

复制代码 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

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复制代码 代码如下:

print x
Traceback (most recent call last):
File "", line 1, in
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
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复制代码 代码如下:

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

复制代码 代码如下:

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

复制代码 代码如下:

if X>Y:
... X,Y = 3,4
... print X,Y
File "", line 3
print X,Y
^
IndentationError: unexpected indent

t = (1,2,3,4)
File "", 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
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

复制代码 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

复制代码 代码如下:

f.next() #
Traceback (most recent call last):
File "", line 1, in
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

复制代码 代码如下:

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

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复制代码 代码如下:

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

【错误分析】接受的变量少了，应该是

复制代码 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')

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

复制代码 代码如下:

mydic={'a':1,'b':2}
mydic['a']
1
mydic['c']
Traceback (most recent call last):
File "", 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

复制代码 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!'

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

复制代码 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

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

复制代码 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:

复制代码 代码如下:

b = Bird()
b.eat()
Ahaha...
b.eat()
No, Thanks!

下面一个子类SingBird,

复制代码 代码如下:

class SingBird(Bird):
def init(self):
self.sound = 'squawk'
def sing(self):
print self.sound

输出结果:

复制代码 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,

复制代码 代码如下:

s.eat()
Traceback (most recent call last):
File "<pyshell#5>", line 1, in
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

复制代码 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

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

复制代码 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
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

复制代码 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...

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

复制代码 代码如下:

T
(1, 2, 3, 4)
T[0] = 22
Traceback (most recent call last):
File "<pyshell#129>", line 1, in
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.

复制代码 代码如下: