Python_常見內置函數_ZenDei技術網路在線

1. 方法註：class（類）是具有相同的屬性和方法的對象的集合。 2. 例子（1）數據/集合類型 str(object=''); str(object=b'', encoding='utf-8', errors='strict') int(x, base=10) float(x=0) comp ...

1. 方法

註：class（類）是具有相同的屬性和方法的對象的集合。

2. 例子

（1）數據/集合類型

str(object=''); str(object=b'', encoding='utf-8', errors='strict')
int(x, base=10)
float(x=0)
complex(real=0, imag=0)

 1 >>> str(123)
 2 '123'
 3 >>> str(['a', 'b', 'c'])
 4 "['a', 'b', 'c']"
 5 >>> str(123).join(['a', 'b', 'c'])
 6 'a123b123c'
 7 >>> int('123')
 8 123
 9 >>> float('123')
10 123.0
11 >>> (0.75).as_integer_ratio()
12 (3, 4)
13 >>> (1.0).is_integer()
14 True
15 >>> complex(1, 2)
16 (1+2j)
17 >>> complex(1, 2).conjugate()
18 (1-2j)

註：str方法，詳情見https://www.cnblogs.com/shz-blog/p/12426630.html

range(stop), range(start, stop[, step])
tuple(iterable=())
list([iterable])
dict(); dict(mapping); dict(iterable); dict(**kwargs)

 1 >>> r = range(40, 1, -3)
 2 >>> t = tuple(r)
 3 >>> l = list(r)
 4 >>> t
 5 (40, 37, 34, 31, 28, 25, 22, 19, 16, 13, 10, 7, 4)
 6 >>> l
 7 [40, 37, 34, 31, 28, 25, 22, 19, 16, 13, 10, 7, 4]
 8 >>> r.count(1)
 9 0
10 >>> r.index(31)
11 3
12 >>> t.count(10)
13 1
14 >>> t.index(31)
15 3
16 >>> l.sort()
17 >>> l
18 [4, 7, 10, 13, 16, 19, 22, 25, 28, 31, 34, 37, 40]
19 >>> dict(a=1, b=2, c=3)
20 {'a': 1, 'b': 2, 'c': 3}
21 >>> dict(zip(list('abc'), [1, 2, 3]))
22 {'a': 1, 'b': 2, 'c': 3}
23 >>> dict([('a', 1), ('b', 2), ('c', 3)])
24 {'a': 1, 'b': 2, 'c': 3}
25 >>> dict(a=1, b=2, c=3).items()
26 dict_items([('a', 1), ('b', 2), ('c', 3)])

註：list方法，詳情見https://www.cnblogs.com/shz-blog/p/12438954.html；

　 dict方法，詳情見https://www.cnblogs.com/shz-blog/p/12456194.html

set([iterable])
frozenset([iterable])

 1 >>> s1 = set('hello')
 2 >>> s1
 3 {'o', 'h', 'e', 'l'}
 4 >>> s1.add(123)
 5 >>> s1
 6 {'o', 'l', 'h', 'e', 123}
 7 >>> s1.discard('o')
 8 >>> s1
 9 {'l', 'h', 'e', 123}
10 >>> s2 = set('lemon')
11 >>> s2
12 {'o', 'l', 'e', 'm', 'n'}
13 >>> s1.update(s2)
14 >>> s1
15 {'o', 'l', 'h', 'e', 'm', 'n', 123}

 1 >>> a = frozenset('hello world')
 2 >>> a
 3 frozenset({'w', 'l', ' ', 'r', 'o', 'h', 'd', 'e'})
 4 >>> b = frozenset(range(5))
 5 >>> b
 6 frozenset({0, 1, 2, 3, 4})
 7 >>> c = frozenset(range(2,7))
 8 >>> c
 9 frozenset({2, 3, 4, 5, 6})
10 >>> b.union(c)    # 並集
11 frozenset({0, 1, 2, 3, 4, 5, 6})
12 >>> b.intersection(c)    # 交集
13 frozenset({2, 3, 4})
14 >>> b.difference(c)    # 差集
15 frozenset({0, 1})
16 >>> c.difference(b)    # 差集
17 frozenset({5, 6})
18 >>> b.symmetric_difference(c)    # 對稱差集
19 frozenset({0, 1, 5, 6})
20 >>> b.isdisjoint(c)    # 是否沒有交集
21 False
22 >>> d = frozenset(range(2,5))
23 >>> d
24 frozenset({2, 3, 4})
25 >>> d.issubset(b)    # 是否被包含
26 True
27 >>> b.issuperset(d)    # 是否包含
28 True
29 >>> e = d.copy()    #複製
30 >>> id(d) == id(e)
31 True

bytearray和bytes

 1 >>> bytes()
 2 b''
 3 >>> bytes(3)
 4 b'\x00\x00\x00'
 5 >>> bytes('abc', 'utf-8')
 6 b'abc'
 7 >>> bytes([1, 2, 3])
 8 b'\x01\x02\x03'
 9 >>> b'abcd'.replace(b'bc', b'XY')
10 b'aXYd'
11 
12 >>> B = b'abc'
13 >>> BA = bytearray(B)
14 >>> BA
15 bytearray(b'abc')
16 >>> [i for i in B]
17 [97, 98, 99]
18 >>> [i for i in BA]
19 [97, 98, 99]
20 >>> B[0] = 65
21 Traceback (most recent call last):
22   File "<pyshell#25>", line 1, in <module>
23     B[0] = 65
24 TypeError: 'bytes' object does not support item assignment
25 >>> BA[0] = 65
26 >>> BA
27 bytearray(b'Abc')

（2）操作

format(value, format_spec='')

　　詳情見https://www.cnblogs.com/shz-blog/p/12422194.html

len(obj)
sorted(iterable, key=None, reverse=False)
reversed(sequence)
slice(stop); slice(start, stop[, step])

 1 >>> L = list('abcde')
 2 >>> L
 3 ['a', 'b', 'c', 'd', 'e']
 4 >>> len(L)
 5 5
 6 >>> sorted(L, reverse=True)
 7 ['e', 'd', 'c', 'b', 'a']
 8 >>> list(reversed(L))
 9 ['e', 'd', 'c', 'b', 'a']
10 >>> L[slice(1, 4, 2)]
11 ['b', 'd']

enumerate(iterable, start=0)
zip(iter1 [,iter2 [...]])
map(func, *iterables)

 1 >>> l1 = [1, 2, 3]
 2 >>> l2 = [4, 5, 6]
 3 >>> l3 = [7, 8, 9, 10]
 4 
 5 >>> list(enumerate(l3))
 6 [(0, 7), (1, 8), (2, 9), (3, 10)]
 7 
 8 >>> list(zip(l1, l2))
 9 [(1, 4), (2, 5), (3, 6)]
10 >>> list(zip(l1, l3))
11 [(1, 7), (2, 8), (3, 9)]
12 >>> list(zip(*zip(l1, l3)))    # *理解為解壓
13 [(1, 2, 3), (7, 8, 9)]
14 
15 >>> list(map(lambda x: x * 3, l1))
16 [3, 6, 9]
17 >>> list(map(lambda x, y: x + y, l1, l2))
18 [5, 7, 9]

（3）輸入輸出

input(prompt=None)
open(file, mode='r', buffering=-1, encoding=None, errors=None, newline=None, closefd=True, opener=None)
print(value, ..., sep=' ', end='\n', file=sys.stdout, flush=False)

1 >>> age = input('請輸入年齡:')
2 請輸入年齡:18
3 >>> age
4 '18'
5 >>> type(age)
6 <class 'str'>

註：open的用法，詳情見https://www.cnblogs.com/sesshoumaru/p/6047046.html；

文件的打開、讀取等各種操作，詳情見https://www.cnblogs.com/hackpig/p/8215786.html

1 >>> print('hello world', 'hello Bunny', sep='\n', end='_'*10)
2 hello world
3 hello Bunny__________

註：flush的用法，參考https://blog.csdn.net/Zhongjie1986/article/details/91890109

（4）數學函數

abs(x)
divmod(x, y)
pow(x, y, z=None)
round(number, ndigits=None)
sum(iterable, start=0)
max(arg1, arg2, *args, *[, key=func]); max(iterable, *[, default=obj, key=func])
min(arg1, arg2, *args, *[, key=func]); min(iterable, *[, default=obj, key=func])

 1 >>> abs(-10)
 2 10
 3 >>> divmod(11, 3)
 4 (3, 2)
 5 >>> pow(2, 3)
 6 8
 7 >>> pow(2, 3, 3)
 8 2
 9 >>> round(1.2345, 2)
10 1.23
11 >>> sum(range(5))
12 10

 1 >>> max(1, 2, 3)
 2 3
 3 >>> max(1, 2, '3')
 4 Traceback (most recent call last):
 5   File "<pyshell#1>", line 1, in <module>
 6     max(1, 2, '3')
 7 TypeError: '>' not supported between instances of 'str' and 'int'
 8 >>> max(1, 2, '3', key=int)
 9 '3'
10 >>> max(-3, 1, 2, key=abs)
11 -3
12 >>> max('123')
13 '3'
14 >>> max([1, 8], [2, 6], [3, 4])
15 [3, 4]
16 >>> couple = ({'name': 'Bunny', 'age': 18, 'salary': 888}, {'name': 'Twan', 'age': 20, 'salary': 666})
17 >>> max(couple, key=lambda x: x['age'])
18 {'name': 'Twan', 'age': 20, 'salary': 666}
19 >>> max((), default=0)
20 0

（5）編碼

bin(number), oct(number), hex(number)
chr(i), ord(c), ascii(obj), repr(obj)

 1 >>> bin(10)
 2 '0b1010'
 3 >>> oct(10)
 4 '0o12'
 5 >>> hex(10)
 6 '0xa'
 7 >>> chr(65)
 8 'A'
 9 >>> ord('A')
10 65
11 >>> ascii('hello world')
12 "'hello world'"
13 >>> repr('hello world')
14 "'hello world'"
15 >>> ascii('你好，世界')
16 "'\\u4f60\\u597d\\uff0c\\u4e16\\u754c'"
17 >>> repr('你好，世界')
18 "'你好，世界'"

（6）判斷

bool(x), all(iterable), any(iterable), callable(object)

 1 >>> all(['a', 'b', 'c'])
 2 True
 3 >>> all(['a', 'b', '', 'c'])
 4 False
 5 >>> all([])
 6 True
 7 >>> any([0, '', False])
 8 False
 9 >>> any([])
10 False
11 >>> callable(str)
12 True
13 >>> callable('hello world')
14 False

（7）迭代器

iter(iterable); iter(callable, sentinel)
next(iterator[, default])
filter(function or None, iterable)

 1 >>> for i in iter(list('abc')):
 2     　　print(i)
 3     
 4 a
 5 b
 6 c
 7 
 8 >>> from random import randint
 9 >>> def guess():
10     return randint(0,10)
11 >>> num = 1
12 >>> for i in iter(guess, 5):
13     print('第%s次猜測，猜測數字為：%s' % (num, i))
14     num += 1
15     
16 第1次猜測，猜測數字為：3
17 第2次猜測，猜測數字為：1

註：猜數字的例子來自http://www.imooc.com/article/287997

 1 >>> i = iter(list('abc'))
 2 >>> next(i)
 3 'a'
 4 >>> next(i)
 5 'b'
 6 >>> next(i)
 7 'c'
 8 >>> next(i)
 9 Traceback (most recent call last):
10   File "<pyshell#27>", line 1, in <module>
11     next(i)
12 StopIteration
13 >>> next(i, 0)
14 0

1 >>> def is_odd(n):
2     return n % 2 == 1
3 
4 >>> oldlist = [i for i in range(1,11)]
5 >>> oldlist
6 [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
7 >>> newlist = list(filter(is_odd, oldlist))
8 >>> newlist
9 [1, 3, 5, 7, 9]

（8）屬性操作

getattr(obj, name[, default])
setattr(obj, name, value)
hasattr(obj, name)
delattr(obj, name)

 1 >>> class Person:
 2     　　name = 'Bunny'
 3     　　age = 18
 4     　　sex = '女'
 5 
 6 >>> Person.name
 7 'Bunny'
 8 >>> Person.country
 9 Traceback (most recent call last):
10   File "<pyshell#6>", line 1, in <module>
11     Person.country
12 AttributeError: type object 'Person' has no attribute 'country'
13 >>> getattr(Person, 'age', 0)
14 18
15 >>> getattr(Person, 'country', 0)
16 0
17 >>> setattr(Person, 'country', 'China')
18 >>> getattr(Person, 'country', 0)
19 'China'
20 >>> delattr(Person, 'sex')
21 >>> hasattr(Person, 'sex')
22 False

（9）輔助函數

dir([object])

1 >>> dir()
2 ['__annotations__', '__builtins__', '__doc__', '__loader__', '__name__', '__package__', '__spec__']
3 >>> dir(dict)
4 ['__class__', '__contains__', '__delattr__', '__delitem__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getitem__', '__gt__', '__hash__', '__init__', '__init_subclass__', '__iter__', '__le__', '__len__', '__lt__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__setitem__', '__sizeof__', '__str__', '__subclasshook__', 'clear', 'copy', 'fromkeys', 'get', 'items', 'keys', 'pop', 'popitem', 'setdefault', 'update', 'values']

help([object])

1 >>> help(hash)
2 Help on built-in function hash in module builtins:
3 
4 hash(obj, /)
5     Return the hash value for the given object.
6     
7     Two objects that compare equal must also have the same hash value, but the
8     reverse is not necessarily true.

hash(obj)

1 >>> hash('hello world')
2 -8331809543453374991
3 >>> hash(tuple('abcde'))
4 5996617995451668254

　　哈希的相關知識點：https://www.cnblogs.com/abdm-989/p/11329122.html

id([object])

1 >>> a = 'hello world'
2 >>> b = a
3 >>> id(a)
4 1873301041520
5 >>> id(b)
6 1873301041520

memoryview(object)

1 >>> a = memoryview(bytearray('abcde', 'utf-8'))
2 >>> a[1]
3 98
4 >>> a[1:3]
5 <memory at 0x0000017F63B83408>
6 >>> a[1:3].tobytes()
7 b'bc'
8 >>> a[1:3].tolist()
9 [98, 99]

優點：memoryview減少記憶體拷貝，優化效率（詳情可參考https://www.hustyx.com/python/222/）

type(object), type(name, bases, dict)
issubclass(cls, class_or_tuple)
isinstance(obj, class_or_tuple)

1 >>> a = 2
2 >>> type(a)
3 <class 'int'>
4 >>> isinstance(a, int)
5 True
6 >>> isinstance(a, str)
7 False
8 >>> isinstance(a, (str, int, list))    # 是元組中的一個就返回True
9 True

 1 >>> class A:
 2　　　　pass
 3 
 4 >>> class B(A):
 5　　　　pass
 6 
 7