Python学习

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str = r"D:\now"
print(str)

------------------------------

D:\now

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print(type(3.14))
print(isinstance(15, int))

-----------------------------------

<class 'float'>
True

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print(3//2)
print(-3**3)
print(3<4<5)

--------------------------

1
-27
True

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x = 6 if 2 > 4 else 7
print(x)

--------------------------------

7

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a = [2,3,4]
print(a)
a = ['2',3,True]
print(a)
print(len(a))
a = []
print(a)

------------------------------

[2, 3, 4]
['2', 3, True]
3
[]

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a = [1,"2",3]
a.append("sss")
print(a)
a.extend(["eee",6])
print(a)
a.insert(1,"one")
print(a)

------------------------------

[1, '2', 3, 'sss']
[1, '2', 3, 'sss', 'eee', 6]
[1, 'one', '2', 3, 'sss', 'eee', 6]

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a = [1,2,3,3]
a.remove(1)
print(a)
a.remove(3)
print(a)

-----------------------

[2, 3, 3]
[2, 3]

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a = [1,2,3]
del a[0]
print(a)
del a
print(a)

------------------------

[2, 3]
Traceback (most recent call last):
  File "D:/python/mysources/test2/test2.py", line 38, in <module>
    print(a)
NameError: name 'a' is not defined

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a = [1,2,3,4,5]
a.pop()
print(a)
print(a.pop())
a.pop(1)
print(a)

----------------------------

[1, 2, 3, 4]
4
[1, 3]

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a = [1,2,3,4]
print(a[1:3])
print(a[:3])
print(a[1:])
print(a[:])
print(a[:-1])
print(a[-3:])

--------------------------

[2, 3]
[1, 2, 3]
[2, 3, 4]
[1, 2, 3, 4]
[1, 2, 3]
[2, 3, 4]

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a = [3,3,1,1,2,4]
print(a.count(3))
print(a.index(1))
print(a.index(3))
print(a.index(1,3))
print(a.index(1,1,2))#左闭右开

------------------------------------

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3
Traceback (most recent call last):
  File "D:/python/mysources/test2/test2.py", line 60, in <module>
    print(a.index(1,1,2))#左闭右开
ValueError: 1 is not in list

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a = [3,5,7,1,2]
b = a[:]
c = a
a.reverse()
print(a)
a.sort()
print(a)
a.sort(reverse=True)
print(a)
print(b)
print(c)

------------------------------------

[2, 1, 7, 5, 3]
[1, 2, 3, 5, 7]
[7, 5, 3, 2, 1]
[3, 5, 7, 1, 2]
[7, 5, 3, 2, 1]

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a = (1,2,'4')
print(a)
a = 1,
print(type(a))
a = (1,)
print(type(a))

-----------------------

(1, 2, '4')
<class 'tuple'>
<class 'tuple'>

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s = '{0} {1} {2}'.format("aaa","bb","c")
print(s)
s = '{0:.2f} {1}'.format(3.266,'ww')
print(s)
s = "%s %c %6.2f" % ('qqq',98,3.145)
print(s)
print('%#o' % 10)
print('%010d' % 52)

---------------------------------

aaa bb c
3.27 ww
qqq b   3.15
0o12
0000000052

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a = list('abc')
print(a)
a = list((2,3,4))
print(a)
a = list((3,5,1,7,3))
print(sorted(a))
print(reversed(a))  #没有改变 a
print(list(reversed(a)))
print(sorted(a,reverse=True))
print(enumerate(a))
print(list(enumerate(a)))
b = [4,2,6]
print(zip(a,b))
print(list(zip(a,b)))

--------------------------------------------

['a', 'b', 'c']
[2, 3, 4]
[1, 3, 3, 5, 7]
<list_reverseiterator object at 0x000001961A58C400>
[3, 7, 1, 5, 3]
[7, 5, 3, 3, 1]
<enumerate object at 0x000001961A59DA68>
[(0, 3), (1, 5), (2, 1), (3, 7), (4, 3)]
<zip object at 0x000001961A59E5C8>
[(3, 4), (5, 2), (1, 6)]

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def func(a):
    'it is a doc'
    print(a)
func(3)
print(func.__doc__)
help(func)

------------------------------

3
it is a doc
Help on function func in module __main__:

func(a)
    it is a doc

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def func(*params , x = 5):
    print(x)
    print(params[1])
def fun(*param , x):
    print(x)
func(2,3,1)
fun(4,5,2,x=7)

---------------------------

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3
7

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a = 5
def fun():
    a = 10
    print(a)
def func():
    global a
    a = 10
fun()
print(a)
func()
print(a)

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5
10

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def fun1(x):
    def fun2(y):
        return x*y
    return fun2
a = fun1(3)
print(type(a))
b = a(5)
print(b)
print(fun1(4)(7))

-------------------------

<class 'function'>
15
28

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def fun1():
    x = 3
    def fun2():
        x *= x
        return x
    return fun2()
print(fun1())

-------------------------

Traceback (most recent call last):
  File "D:/python/mysources/test2/test2.py", line 155, in <module>
    print(fun1())
  File "D:/python/mysources/test2/test2.py", line 154, in fun1
    return fun2()
  File "D:/python/mysources/test2/test2.py", line 152, in fun2
    x *= x
UnboundLocalError: local variable 'x' referenced before assignment

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def fun1():
    x = [3]
    def fun2():
        x[0] *= x[0]   #容器化
        return x[0]
    return fun2()
print(fun1())

-----------------------------------

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def fun1():
    x = 3
    def fun2():
        nonlocal x
        x *= x
        return x
    return fun2()
print(fun1())

---------------------------------------

9

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a = lambda x,y : x + y
print(a)
print(type(a))
print(a(3,6))

------------------------

<function <lambda> at 0x000001418C837F28>
<class 'function'>
9

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print(list(filter(lambda x:x%2,[1,2,3,4,5])))
print(list(map(lambda x:x*2+1,[1,2,3,4,7])))

--------------------------------------------------------

[1, 3, 5]
[3, 5, 7, 9, 15]

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a = dict((('2','aaa') , (3,'vvv') , ('ss',7)))
print(a)
a = dict(a='222' , sss=99) #key是字符串
print(a)

----------------------------------------------

{'ss': 7, '2': 'aaa', 3: 'vvv'}
{'a': '222', 'sss': 99}

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a = {}
print(a.fromkeys((1,2,3),'num')) #产生新的但不改变a
print(a)
print(a.fromkeys((1,3,4),('a','b')))
print(a.fromkeys((1,3,4),('a','b','d')))
print(a.fromkeys(range(4),'s'))

-------------------------------------------------

{1: 'num', 2: 'num', 3: 'num'}
{}
{1: ('a', 'b'), 3: ('a', 'b'), 4: ('a', 'b')}
{1: ('a', 'b', 'd'), 3: ('a', 'b', 'd'), 4: ('a', 'b', 'd')}
{0: 's', 1: 's', 2: 's', 3: 's'}

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a = {}
b = a.fromkeys((1,3,4),'s')
print(b.keys())
print(b.values())
print(dict(b.items()))
print(b.get(7,'x'))
print(b.get(3,'x'))

----------------------------

dict_keys([1, 3, 4])
dict_values(['s', 's', 's'])
{1: 's', 3: 's', 4: 's'}
x
s

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a = {1:2}
b = a
a = {}
print(a)
print(b)
b = a
a.clear()
print(b)

-----------------------------

{}
{1: 2}
{}

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a = {1:'one' , 2:'to' , 3:'san'}
b = a
c = a.copy()
print(id(a))
print(id(b))
print(id(c))
a.popitem() #随机返回并删除最后一组的键值对
print(a)
a.setdefault(4,'for')
print(a)
d = {'5':'five' , 2:'two'}
a.update(d)
print(a)

----------------------

2597077552072
2597077552072
2597077552200
{2: 'to', 3: 'san'}
{2: 'to', 3: 'san', 4: 'for'}
{2: 'two', 3: 'san', 4: 'for', '5': 'five'}

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import sys
std_out = sys.stdout #备份
std_in = sys.stdin #备份
sys.stdout = open('out.txt','w')
sys.stdin = open('in.txt','r')
n,m = map(int,input().split())
print(n+m)
sys.stdout.close()
sys.stdin.close()

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try:
    print(2)
    print(1+'2')
except (NameError , TypeError) as reason:
    print(reason)

------------------------------------------

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unsupported operand type(s) for +: 'int' and 'str'

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try:
    print(2)
    print(1+'2')
except NameError as reason:
    print('not defined' + str(reason))
except TypeError as reason:
    print(reason)
    
-----------------------------------------

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unsupported operand type(s) for +: 'int' and 'str'

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try:
    print(2)
    print(1+'2')
except (NameError, TypeError) as reason:
    print(reason)
finally:
    print('aaa')

------------------------------------

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unsupported operand type(s) for +: 'int' and 'str'
aaa

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try:
    print(2)
    print(1+'2')
except (NameError , TypeError) as reason:
    print(reason)
else:
    print('no error')
finally:
    print('aaa')

-------------------

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unsupported operand type(s) for +: 'int' and 'str'
aaa

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class Mylist(list):
    pass
ml = Mylist()
ml.append(1)
ml.append(3)
ml.append(2)
ml.sort()
print(ml)

---------------------

[1, 2, 3]

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class Person:
    name = None
    school = 'hhu'
    def fun1(self):
        print(self.name)
    def fun2(self):
        print(self.school)
p = Person()
p.name = 'qq'
p.fun1()
p.fun2()

---------------------

qq
hhu

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class Person:
    def __init__(self,name,gender):
        self.name = name
        self.gender = gender
    def doit(self):
        print(self.name,self.gender)
p = Person('qq','female')
p.doit()

-----------------------------

qq female

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class Person:
    __name = 'aaa'
    def getName(self):
        return self.__name
p = Person()
print(p.getName())
print(p._Person__name)
print(p.__name)
print(p.name)

------------------

aaa
aaa
Traceback (most recent call last):
  File "D:/python/mysources/test2/test2.py", line 282, in <module>
    print(p.__name)
AttributeError: 'Person' object has no attribute '__name'

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class A:
    f = 1
    def x(self):
        print('xxx')

a = A()
b = A()
c = A()
c.f += 1
print(c.f)
print(a.f)
A.f += 100
print(a.f)
print(b.f)
print(c.f)
d = A()
print(d.x())
d.x = 1
print(d.x)
print(d.x())

-------------------

Traceback (most recent call last):
  File "D:/python/mysources/test2/test2.py", line 305, in <module>
    print(d.x())
TypeError: 'int' object is not callable
2
1
101
101
2
xxx
None
1

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n = float(input())
print('%.2f' % (n + 0.001))

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while True:
    try:
        pass
    except:
        break

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a = [[0] * 5 for i in range(10)]
print(a)

------------------------------

[[0, 0, 0, 0, 0], [0, 0, 0, 0, 0], [0, 0, 0, 0, 0], [0, 0, 0, 0, 0], [0, 0, 0, 0, 0], [0, 0, 0, 0, 0], [0, 0, 0, 0, 0], [0, 0, 0, 0, 0], [0, 0, 0, 0, 0], [0, 0, 0, 0, 0]]