Python內(nèi)置函數(shù)(63個(gè))

1.abs()

絕對(duì)值或復(fù)數(shù)的模

In [1]: abs(-6)
Out[1]: 6

2.all()

接受一個(gè)迭代器月腋，如果迭代器的所有元素都為真岳链，那么返回True矾策，否則返回False

In [2]: all([1,0,3,6])
Out[2]: False

In [3]: all([1,2,3])
Out[3]: True

3.any()

接受一個(gè)迭代器稿黄，如果迭代器里有一個(gè)元素為真尝苇，那么返回True愧旦，否則返回False

In [4]: any([0,0,0,[]])
Out[4]: False

In [5]: any([0,0,1])
Out[5]: True

4.ascii()

調(diào)用對(duì)象的repr() 方法世剖，獲得該方法的返回值

In [30]: class Student():
    ...:     def __init__(self,id,name):
    ...:         self.id = id
    ...:         self.name = name
    ...:     def __repr__(self):
    ...:         return 'id = '+self.id +', name = '+self.name

In [32]: xiaoming = Student('01','xiaoming')
In [33]: print(xiaoming)
id = 001, name = xiaoming

In [34]: ascii(xiaoming)
Out[34]: 'id = 001, name = xiaoming'

5.bin()

將十進(jìn)制轉(zhuǎn)換為二進(jìn)制

In [35]: bin(10)
Out[35]: '0b1010'

6.oct()

將十進(jìn)制轉(zhuǎn)換為八進(jìn)制

In [36]: oct(9)
Out[36]: '0o11'

7.hex()

將十進(jìn)制轉(zhuǎn)換為十六進(jìn)制

In [37]: hex(15)
Out[37]: '0xf'

8.bool()

測(cè)試一個(gè)對(duì)象是True, 還是False.

In [38]: bool([0,0,0])
Out[38]: True

In [39]: bool([])
Out[39]: False

In [40]: bool([1,0,1])
Out[40]: True

9.bytes()

將一個(gè)字符串轉(zhuǎn)換成字節(jié)類型

In [44]: s = "apple"

In [45]: bytes(s,encoding='utf-8')
Out[45]: b'apple'

10.str()

將字符類型、數(shù)值類型等轉(zhuǎn)換為字符串類型

In [46]: integ = 100

In [47]: str(integ)
Out[47]: '100'

11.callable()

判斷對(duì)象是否可以被調(diào)用笤虫，能被調(diào)用的對(duì)象就是一個(gè)callable 對(duì)象旁瘫，比如函數(shù) str, int 等都是可被調(diào)用的，但是例子4 中xiaoming這個(gè)實(shí)例是不可被調(diào)用的：

In [48]: callable(str)
Out[48]: True

In [49]: callable(int)
Out[49]: True

In [50]: xiaoming
Out[50]: id = 001, name = xiaoming

In [51]: callable(xiaoming)
Out[51]: False

12.chr()

查看十進(jìn)制整數(shù)對(duì)應(yīng)的ASCII字符

In [54]: chr(65)
Out[54]: 'A'

13.ord()

查看某個(gè)ascii對(duì)應(yīng)的十進(jìn)制數(shù)

In [60]: ord('A')
Out[60]: 65

14.classmethod()

classmethod 修飾符對(duì)應(yīng)的函數(shù)不需要實(shí)例化琼蚯，不需要 self 參數(shù)酬凳，但第一個(gè)參數(shù)需要是表示自身類的 cls 參數(shù)，可以來(lái)調(diào)用類的屬性遭庶，類的方法宁仔，實(shí)例化對(duì)象等。

In [66]: class Student():
    ...:     def __init__(self,id,name):
    ...:         self.id = id
    ...:         self.name = name
    ...:     def __repr__(self):
    ...:         return 'id = '+self.id +', name = '+self.name
    ...:     @classmethod
    ...:     def f(cls):
    ...:         print(cls)

15.complie()

將字符串編譯成python 能識(shí)別或可以執(zhí)行的代碼峦睡，也可以將文字讀成字符串再編譯翎苫。

In [74]: s  = "print('helloworld')"

In [75]: r = compile(s,"<string>", "exec")

In [76]: r
Out[76]: <code object <module> at 0x0000000005DE75D0, file "<string>", line 1>

In [77]: exec(r)
helloworld

16.complex()

創(chuàng)建一個(gè)復(fù)數(shù)

In [81]: complex(1,2)
Out[81]: (1+2j)

17.delattr()

刪除對(duì)象的屬性

In [87]: delattr(xiaoming,'id')

In [88]: hasattr(xiaoming,'id')
Out[88]: False

18.dict()

創(chuàng)建數(shù)據(jù)字典

In [92]: dict()
Out[92]: {}

In [93]: dict(a='a',b='b')
Out[93]: {'a': 'a', 'b': 'b'}

In [94]: dict(zip(['a','b'],[1,2]))
Out[94]: {'a': 1, 'b': 2}

In [95]: dict([('a',1),('b',2)])
Out[95]: {'a': 1, 'b': 2}

19.dir()

不帶參數(shù)時(shí)返回當(dāng)前范圍內(nèi)的變量，方法和定義的類型列表榨了；帶參數(shù)時(shí)返回參數(shù)的屬性煎谍，方法列表。

In [96]: dir(xiaoming)
Out[96]:
['__class__',
 '__delattr__',
 '__dict__',
 '__dir__',
 '__doc__',
 '__eq__',
 '__format__',
 '__ge__',
 '__getattribute__',
 '__gt__',
 '__hash__',
 '__init__',
 '__init_subclass__',
 '__le__',
 '__lt__',
 '__module__',
 '__ne__',
 '__new__',
 '__reduce__',
 '__reduce_ex__',
 '__repr__',
 '__setattr__',
 '__sizeof__',
 '__str__',
 '__subclasshook__',
 '__weakref__',

 'name']

20.divmod()

分別取商和余數(shù)

In [97]: divmod(10,3)
Out[97]: (3, 1)

21.enumerate()

返回一個(gè)可以枚舉的對(duì)象龙屉，該對(duì)象的next()方法將返回一個(gè)元組呐粘。

In [98]: s = ["a","b","c"]
    ...: for i ,v in enumerate(s,1):
    ...:     print(i,v)
    ...:
1 a
2 b
3 c

22.eval()

將字符串str 當(dāng)成有效的表達(dá)式來(lái)求值并返回計(jì)算結(jié)果取出字符串中內(nèi)容

In [99]: s = "1 + 3 +5"
    ...: eval(s)
    ...:
Out[99]: 9

23.exec()

執(zhí)行字符串或complie方法編譯過(guò)的字符串，沒(méi)有返回值

In [74]: s  = "print('helloworld')"

In [75]: r = compile(s,"<string>", "exec")

In [76]: r
Out[76]: <code object <module> at 0x0000000005DE75D0, file "<string>", line 1>

In [77]: exec(r)
helloworld

24.filter()

過(guò)濾器，構(gòu)造一個(gè)序列事哭，等價(jià)于

[ item for item in iterables if function(item)]

在函數(shù)中設(shè)定過(guò)濾條件漫雷，逐一循環(huán)迭代器中的元素，將返回值為T(mén)rue時(shí)的元素留下鳍咱，形成一個(gè)filter類型數(shù)據(jù)降盹。

In [101]: fil = filter(lambda x: x>10,[1,11,2,45,7,6,13])

In [102]: list(fil)
Out[102]: [11, 45, 13]

25.float()

將一個(gè)字符串或整數(shù)轉(zhuǎn)換為浮點(diǎn)數(shù)

In [103]: float(3)
Out[103]: 3.0

26.format()

格式化輸出字符串，format(value, format_spec)實(shí)質(zhì)上是調(diào)用了value的format(format_spec)方法谤辜。

In [104]: print("i am {0},age{1}".format("tom",18))
i am tom,age18

27.frozenset()

創(chuàng)建一個(gè)不可修改的集合蓄坏。

In [105]: frozenset([1,1,3,2,3])
Out[105]: frozenset({1, 2, 3})

28.getattr()

獲取對(duì)象的屬性

In [106]: getattr(xiaoming,'name')
Out[106]: 'xiaoming'

29.globals()

返回一個(gè)描述當(dāng)前全局變量的字典

30.hasattr()

In [110]: hasattr(xiaoming,'name')
Out[110]: True

In [111]: hasattr(xiaoming,'id')
Out[111]: False

31.hash()

返回對(duì)象的哈希值

In [112]: hash(xiaoming)
Out[112]: 6139638

32.help()

返回對(duì)象的幫助文檔

In [113]: help(xiaoming)
Help on Student in module __main__ object:

class Student(builtins.object)
 |  Methods defined here:
 |
 |  __init__(self, id, name)
 |
 |  __repr__(self)
 |
 |  ----------------------------------------------------------------------
 |  Data descriptors defined here:
 |
 |  __dict__
 |      dictionary for instance variables (if defined)
 |
 |  __weakref__
 |      list of weak references to the object (if defined)

33.id()

返回對(duì)象的內(nèi)存地址

In [115]: id(xiaoming)
Out[115]: 98234208

34.input()

獲取用戶輸入內(nèi)容

In [116]: input()
aa
Out[116]: 'aa'

35.int()

int(x, base =10) , x可能為字符串或數(shù)值，將x 轉(zhuǎn)換為一個(gè)普通整數(shù)丑念。如果參數(shù)是字符串涡戳，那么它可能包含符號(hào)和小數(shù)點(diǎn)。如果超出了普通整數(shù)的表示范圍脯倚，一個(gè)長(zhǎng)整數(shù)被返回渔彰。

In [120]: int('12',16)
Out[120]: 18

36.isinstance(object, classinfo)

判斷object是否為類classinfo的實(shí)例，是返回true

In [20]: class Student():
    ...:     ...:     def __init__(self,id,name):
    ...:     ...:         self.id = id
    ...:     ...:         self.name = name
    ...:     ...:     def __repr__(self):
    ...:     ...:         return 'id = '+self.id +', name = '+self.name
    ...:

In [21]: xiaoming = Student('001','xiaoming')

In [22]: isinstance(xiaoming,Student)
Out[22]: True

37.issubclass(class, classinfo)

如果class是classinfo類的子類推正，返回True：

In [27]: class undergraduate(Student):
    ...:     def studyClass(self):
    ...:         pass
    ...:     def attendActivity(self):
    ...:         pass
    ...:

In [28]: issubclass(undergraduate,Student)
Out[28]: True

In [29]: issubclass(object,Student)
Out[29]: False

In [30]: issubclass(Student,object)
Out[30]: True

如果class是classinfo元組中某個(gè)元素的子類恍涂，也會(huì)返回True

In [26]: issubclass(int,(int,float))
Out[26]: True

38.iter(object, sentinel)

返回一個(gè)可迭代對(duì)象, sentinel可省略

In [72]: lst = [1,3,5]

In [73]: for i in iter(lst):
    ...:     print(i)
    ...:
1
3
5

sentinel 理解為迭代對(duì)象的哨兵，一旦迭代到此元素植榕，立即終止：

In [81]: class TestIter(object):
    ...:         def __init__(self):
    ...:             self.l=[1,3,2,3,4,5]
    ...:             self.i=iter(self.l)
    ...:         def __call__(self):  #定義了__call__方法的類的實(shí)例是可調(diào)用的
    ...:             item = next(self.i)
    ...:             print ("__call__ is called,which would return",item)
    ...:             return item
    ...:         def __iter__(self): #支持迭代協(xié)議(即定義有__iter__()函數(shù))
    ...:             print ("__iter__ is called!!")
    ...:             return iter(self.l)
    ...:

In [82]:     t = TestIter()
    ...:     t1 = iter(t, 3)
    ...:     for i in t1:
    ...:         print(i)
    ...:
__call__ is called,which would return 1
1
__call__ is called,which would return 3

39.len(s)

返回對(duì)象的長(zhǎng)度（元素個(gè)數(shù)）

In [83]: dic = {'a':1,'b':3}

In [84]: len(dic)
Out[84]: 2

40.list([iterable])

返回可變序列類型

In [85]: list(map(lambda x: x%2==1, [1,3,2,4,1]))
Out[85]: [True, True, False, False, True]

41.map(function, iterable, …)

返回一個(gè)將 function 應(yīng)用于 iterable 中每一項(xiàng)并輸出其結(jié)果的迭代器：

In [85]: list(map(lambda x: x%2==1, [1,3,2,4,1]))
Out[85]: [True, True, False, False, True]

可以傳入多個(gè)iterable對(duì)象再沧，輸出長(zhǎng)度等于最短序列的長(zhǎng)度：

In [88]: list(map(lambda x,y: x%2==1 and y%2==0, [1,3,2,4,1],[3,2,1,2]))
Out[88]: [False, True, False, False]

42.max(iterable,*[, key, default])

返回最大值：

In [99]: max(3,1,4,2,1)
Out[99]: 4

In [100]: max((),default=0)
Out[100]: 0

In [89]: di = {'a':3,'b1':1,'c':4}
In [90]: max(di)
Out[90]: 'c'

In [102]: a = [{'name':'xiaoming','age':18,'gender':'male'},{'name':'
     ...: xiaohong','age':20,'gender':'female'}]
In [104]: max(a,key=lambda x: x['age'])
Out[104]: {'name': 'xiaohong', 'age': 20, 'gender': 'female'}

43.min(iterable,*[, key, default])

返回最小值

44.memoryview(obj)

返回由給定實(shí)參創(chuàng)建的“內(nèi)存視圖”對(duì)象， Python 代碼訪問(wèn)一個(gè)對(duì)象的內(nèi)部數(shù)據(jù)尊残，只要該對(duì)象支持 緩沖區(qū)協(xié)議 而無(wú)需進(jìn)行拷貝

45.next(iterator,[, default])

返回可迭代對(duì)象的下一個(gè)元素

In [129]: it = iter([5,3,4,1])

In [130]: next(it)
Out[130]: 5

In [131]: next(it)
Out[131]: 3

In [132]: next(it)
Out[132]: 4

In [133]: next(it)
Out[133]: 1

In [134]: next(it,0) #迭代到頭炒瘸，默認(rèn)返回值為0
Out[134]: 0

In [135]: next(it)
----------------------------------------------------------------------
StopIteration                        Traceback (most recent call last)
<ipython-input-135-bc1ab118995a> in <module>
----> 1 next(it)

StopIteration:

46.object()

返回一個(gè)沒(méi)有特征的新對(duì)象。object 是所有類的基類寝衫。

In [137]: o = object()

In [138]: type(o)
Out[138]: object

47.open(file)

返回文件對(duì)象

In [146]: fo = open('D:/a.txt',mode='r', encoding='utf-8')

In [147]: fo.read()
Out[147]: '\ufefflife is not so long,\nI use Python to play.'

mode取值表：

48.pow(base, exp[, mod])

base為底的exp次冪，如果mod給出事富，取余

In [149]: pow(3, 2, 4)
Out[149]: 1

49.print(objects)

打印對(duì)象技俐，此函數(shù)不解釋

50.class property(fget=None, fset=None, fdel=None, doc=None)

返回 property 屬性，典型的用法：

class C:
    def __init__(self):
        self._x = None

    def getx(self):
        return self._x

    def setx(self, value):
        self._x = value

    def delx(self):
        del self._x
    # 使用property類創(chuàng)建 property 屬性
    x = property(getx, setx, delx, "I'm the 'x' property.")

使用python裝飾器统台，實(shí)現(xiàn)與上完全一樣的效果代碼：

class C:
    def __init__(self):
        self._x = None

    @property
    def x(self):
        return self._x

    @x.setter
    def x(self, value):
        self._x = value

    @x.deleter
    def x(self):
        del self._x

51.range(stop)

range(start, stop[,step])

生成一個(gè)不可變序列：

In [153]: range(11)
Out[153]: range(0, 11)

In [154]: range(0,11,1)
Out[154]: range(0, 11)

52.reversed(seq)

返回一個(gè)反向的 iterator:

In [155]: rev = reversed([1,4,2,3,1])

In [156]: for i in rev:
     ...:     print(i)
     ...:
1
3
2
4
1

53.round(number[, ndigits])

四舍五入雕擂，ndigits代表小數(shù)點(diǎn)后保留幾位：

In [157]: round(10.0222222, 3)
Out[157]: 10.022

54.class set([iterable])

返回一個(gè)set對(duì)象，可實(shí)現(xiàn)去重：

In [159]: a = [1,4,2,3,1]

In [160]: set(a)
Out[160]: {1, 2, 3, 4}

55.class slice(stop)

class slice(start, stop[, step])

返回一個(gè)表示由 range(start, stop, step) 所指定索引集的 slice對(duì)象

In [170]: a = [1,4,2,3,1]

In [171]: a[slice(0,5,2)] #等價(jià)于a[0:5:2]
Out[171]: [1, 2, 1]

56.sorted(iterable, *, key=None, reverse=False)

排序：

In [174]: a = [1,4,2,3,1]

In [175]: sorted(a,reverse=True)
Out[175]: [4, 3, 2, 1, 1]

In [178]: a = [{'name':'xiaoming','age':18,'gender':'male'},{'name':'
     ...: xiaohong','age':20,'gender':'female'}]
In [180]: sorted(a,key=lambda x: x['age'],reverse=False)
Out[180]:
[{'name': 'xiaoming', 'age': 18, 'gender': 'male'},
 {'name': 'xiaohong', 'age': 20, 'gender': 'female'}]

57. @``staticmethod`

將方法轉(zhuǎn)換為靜態(tài)方法贱勃，不做解釋

58.vars()

返回模塊井赌、類谤逼、實(shí)例或任何其它具有 __dict__屬性的對(duì)象的 __dict__ 屬性

In [2]: vars()
Out[2]:
{'__name__': '__main__',
 '__doc__': 'Automatically created module for IPython interactive environment',
 '__package__': None,
 '__loader__': None,
 '__spec__': None,
 '__builtin__': <module 'builtins' (built-in)>,
 '__builtins__': <module 'builtins' (built-in)>,
 '_ih': ['', 'vars([1,2,3])', 'vars()'],
 '_oh': {},
 '_dh': ['C:\\Windows\\system32'],
 'In': ['', 'vars([1,2,3])', 'vars()'],
 'Out': {},
 'get_ipython': <bound method InteractiveShell.get_ipython of <IPython.terminal.interactiveshell.TerminalInteractiveShell object at 0x0000026004D91C50>>,
 'exit': <IPython.core.autocall.ExitAutocall at 0x26006011048>,
 'quit': <IPython.core.autocall.ExitAutocall at 0x26006011048>,
 '_': '',
 '__': '',
 '___': '',
 '_i': 'vars([1,2,3])',
 '_ii': '',
 '_iii': '',
 '_i1': 'vars([1,2,3])',
 '_i2': 'vars()'}

59.sum(iterable, /, start=0)

求和：

In [181]: a = [1,4,2,3,1]

In [182]: sum(a)
Out[182]: 11

In [185]: sum(a,10) #求和的初始值為10
Out[185]: 21

60.super([type[, object-or-type]])

返回一個(gè)代理對(duì)象，它會(huì)將方法調(diào)用委托給 type 的父類或兄弟類

61.tuple([iterable])

雖然被稱為函數(shù)仇穗，但 tuple 實(shí)際上是一個(gè)不可變的序列類型

62.class type(object)

class type(name, bases, dict)

傳入一個(gè)參數(shù)時(shí)流部，返回 object 的類型：

In [186]: type(xiaoming)
Out[186]: __main__.Student

In [187]: type(tuple())
Out[187]: tuple

63.zip(*iterables)

創(chuàng)建一個(gè)聚合了來(lái)自每個(gè)可迭代對(duì)象中的元素的迭代器：

In [188]: x = [3,2,1]
In [189]: y = [4,5,6]
In [190]: list(zip(y,x))
Out[190]: [(4, 3), (5, 2), (6, 1)]


In [191]: a = range(5)
In [192]: b = list('abcde')
In [193]: b
Out[193]: ['a', 'b', 'c', 'd', 'e']
In [194]: [str(y) + str(x) for x,y in zip(a,b)]
Out[194]: ['a0', 'b1', 'c2', 'd3', 'e4']