內(nèi)置函數(shù)就是Python給你提供的, 拿來直接用的函數(shù)，比如print.，input等。截止到python版本3.6.2 python一共提供了68個(gè)內(nèi)置函數(shù)，我將它們分成 12 類，方便你學(xué)習(xí)。
ss="dp-xml">ss="alt">#68個(gè)內(nèi)置函數(shù)# abs() dict() help() min() setattr()# all() dir() hex() next() slice() # any() divmod() id() object() sorted() # ascii() enumerate() input() oct() staticmethod() # bin() eval() int() open() str() # bool() exec() isinstance() ord() sum() # bytearray() ?lter() issubclass() pow() super() # bytes() ?oat() iter() print() tuple() # callable() format() len() property() type() # chr() frozenset() list() range() vars() # classmethod() getattr() locals() repr() zip() # compile() globals() map() reversed() __import__() # complex() hasattr() max() round() # delattr() hash() memoryview() set() 
1. 和數(shù)字相關(guān)
(1) 數(shù)據(jù)類型
- bool : 布爾型(True,False)
- int : 整型(整數(shù))
- float : 浮點(diǎn)型(小數(shù))
- complex : 復(fù)數(shù)
(2) 進(jìn)制轉(zhuǎn)換
- bin() 將給的參數(shù)轉(zhuǎn)換成二進(jìn)制
- otc() 將給的參數(shù)轉(zhuǎn)換成八進(jìn)制
- hex() 將給的參數(shù)轉(zhuǎn)換成十六進(jìn)制
ss="dp-xml">ss="alt">print(bin(10)) # 二進(jìn)制:0b1010 ss="">print(hex(10)) # 十六進(jìn)制:0xa ss="alt">print(oct(10)) # 八進(jìn)制:0o12
(3) 數(shù)學(xué)運(yùn)算
- abs() 返回絕對(duì)值
- divmode() 返回商和余數(shù)
- round() 四舍五入
- pow(a, b) 求a的b次冪, 如果有三個(gè)參數(shù). 則求完次冪后對(duì)第三個(gè)數(shù)取余
- sum() 求和
- min() 求最小值
- max() 求最大值
ss="dp-xml">ss="alt">print(abs(-2)) # 絕對(duì)值:2 ss="">print(divmod(20,3)) # 求商和余數(shù):(6,2) ss="alt">print(round(4.50)) # 五舍六入:4 ss="">print(round(4.51)) #5 ss="alt">print(pow(10,2,3)) # 如果給了第三個(gè)參數(shù). 表示最后取余:1 ss="">print(sum([1,2,3,4,5,6,7,8,9,10])) # 求和:55 ss="alt">print(min(5,3,9,12,7,2)) #求最小值:2 ss="">print(max(7,3,15,9,4,13)) #求最大值:15
2. 和數(shù)據(jù)結(jié)構(gòu)相關(guān)
(1) 序列
a. 列表和元組
- list() 將一個(gè)可迭代對(duì)象轉(zhuǎn)換成列表
- tuple() 將一個(gè)可迭代對(duì)象轉(zhuǎn)換成元組
ss="dp-xml">ss="alt">print(list((1,2,3,4,5,6))) #[1, 2, 3, 4, 5, 6] ss="">print(tuple([1,2,3,4,5,6])) #(1, 2, 3, 4, 5, 6)
b. 相關(guān)內(nèi)置函數(shù)
reversed() 將一個(gè)序列翻轉(zhuǎn), 返回翻轉(zhuǎn)序列的迭代器
slice() 列表的切片
ss="dp-xml">ss="alt">ss="attribute">lst = ss="attribute-value">"你好啊" ss="">ss="attribute">it = ss="attribute-value">reversed(lst) # 不會(huì)改變?cè)斜? 返回一個(gè)迭代器, 設(shè)計(jì)上的一個(gè)規(guī)則 ss="alt">print(list(it)) #['啊', '好', '你'] ss="">ss="attribute">lst = [1, 2, 3, 4, 5, 6, 7] ss="alt">print(lst[1:3:1]) #[2,3] ss="">ss="attribute">s = ss="attribute-value">slice(1, 3, 1) # 切片用的 ss="alt">print(lst[s]) #[2,3]
c. 字符串
-
- str() 將數(shù)據(jù)轉(zhuǎn)化成字符串
ss="dp-xml">ss="alt">print(str(123)+'456') #123456 ss="">format() 與具體數(shù)據(jù)相關(guān), 用于計(jì)算各種小數(shù), 精算等.
ss="dp-xml">ss="alt">ss="attribute">s = ss="attribute-value">"hello world!" ss="">print(format(s, "^20")) #劇中 ss="alt">print(format(s, "ss="tag"><ss="tag-name">20")) #左對(duì)齊 ss="">print(format(s, "ss="tag">>20")) #右對(duì)齊 ss="alt"># hello world! ss=""># hello world! ss="alt"># hello world! ss="">print(format(3, 'b' )) # 二進(jìn)制:11 ss="alt">print(format(97, 'c' )) # 轉(zhuǎn)換成unicode字符:a ss="">print(format(11, 'd' )) # ?進(jìn)制:11 ss="alt">print(format(11, 'o' )) # 八進(jìn)制:13 ss="">print(format(11, 'x' )) # 十六進(jìn)制(?寫字母):b ss="alt">print(format(11, 'X' )) # 十六進(jìn)制(大寫字母):B ss="">print(format(11, 'n' )) # 和d?樣:11 ss="alt">print(format(11)) # 和d?樣:11 ss=""> ss="alt">print(format(123456789, 'e' )) # 科學(xué)計(jì)數(shù)法. 默認(rèn)保留6位小數(shù):1.234568e+08 ss="">print(format(123456789, '0.2e' )) # 科學(xué)計(jì)數(shù)法. 保留2位小數(shù)(小寫):1.23e+08 ss="alt">print(format(123456789, '0.2E' )) # 科學(xué)計(jì)數(shù)法. 保留2位小數(shù)(大寫):1.23E+08 ss="">print(format(1.23456789, 'f' )) # 小數(shù)點(diǎn)計(jì)數(shù)法. 保留6位小數(shù):1.234568 ss="alt">print(format(1.23456789, '0.2f' )) # 小數(shù)點(diǎn)計(jì)數(shù)法. 保留2位小數(shù):1.23 ss="">print(format(1.23456789, '0.10f')) # 小數(shù)點(diǎn)計(jì)數(shù)法. 保留10位小數(shù):1.2345678900 ss="alt">print(format(1.23456789e+3, 'F')) # 小數(shù)點(diǎn)計(jì)數(shù)法. 很大的時(shí)候輸出INF:1234.567890
- bytes() 把字符串轉(zhuǎn)化成bytes類型
ss="dp-xml">ss="alt">ss="attribute">bs = ss="attribute-value">bytes("今天吃飯了嗎", ss="attribute">encoding=ss="attribute-value">"utf-8") ss="">print(bs) #b'\xe4\xbb\x8a\xe5\xa4\xa9\xe5\x90\x83\xe9\xa5\xad\xe4\xba\x86\xe5\x90\x97' ss="alt"> bytearray() 返回一個(gè)新字節(jié)數(shù)組. 這個(gè)數(shù)字的元素是可變的, 并且每個(gè)元素的值得范圍是[0,256) ss=""> ss="alt">ss="attribute">ret = ss="attribute-value">bytearray("alex" ,ss="attribute">encoding =ss="attribute-value">'utf-8') ss="">print(ret[0]) #97 ss="alt">print(ret) #bytearray(b'alex') ss="">ret[0] = 65 #把65的位置A賦值給ret[0] ss="alt">print(str(ret)) #bytearray(b'Alex')
- ord() 輸入字符找?guī)ё址幋a的位置
- chr() 輸入位置數(shù)字找出對(duì)應(yīng)的字符
- ascii() 是ascii碼中的返回該值 不是就返回u
ss="dp-xml">ss="alt">print(ord('a')) # 字母a在編碼表中的碼位:97 ss="">print(ord('中')) # '中'字在編碼表中的位置:20013 ss="alt"> ss="">print(chr(65)) # 已知碼位,求字符是什么:A ss="alt">print(chr(19999)) #丟 ss=""> ss="alt">for i in range(65536): #打印出0到65535的字符 ss=""> print(chr(i), ss="attribute">end=ss="attribute-value">" ") ss="alt"> ss="">print(ascii("@")) #'@'
- repr() 返回一個(gè)對(duì)象的string形式
ss="dp-xml">ss="alt">ss="attribute">s = ss="attribute-value">"今天n吃了%s頓t飯" % 3 ss="">print(s)#今天# 吃了3頓 飯 ss="alt">print(repr(s)) # 原樣輸出,過濾掉轉(zhuǎn)義字符 n t r 不管百分號(hào)% ss="">#'今天n吃了3頓t飯'
(2) 數(shù)據(jù)集合
- 字典：dict 創(chuàng)建一個(gè)字典
- 集合：set 創(chuàng)建一個(gè)集合
frozenset() 創(chuàng)建一個(gè)凍結(jié)的集合，凍結(jié)的集合不能進(jìn)行添加和刪除操作。
(3) 相關(guān)內(nèi)置函數(shù)
- len() 返回一個(gè)對(duì)象中的元素的個(gè)數(shù)
- sorted() 對(duì)可迭代對(duì)象進(jìn)行排序操作 (lamda)
a. 語法：sorted(Iterable, key=函數(shù)(排序規(guī)則), reverse=False)
- Iterable: 可迭代對(duì)象
- key: 排序規(guī)則(排序函數(shù)), 在sorted內(nèi)部會(huì)將可迭代對(duì)象中的每一個(gè)元素傳遞給這個(gè)函數(shù)的參數(shù). 根據(jù)函數(shù)運(yùn)算的結(jié)果進(jìn)行排序
- reverse: 是否是倒敘. True: 倒敘, False: 正序
ss="dp-xml">ss="alt">ss="attribute">lst = [5,7,6,12,1,13,9,18,5] ss="">lst.sort() # sort是list里面的一個(gè)方法 ss="alt">print(lst) #[1, 5, 5, 6, 7, 9, 12, 13, 18] ss=""> ss="alt">ss="attribute">ll = ss="attribute-value">sorted(lst) # 內(nèi)置函數(shù). 返回給你一個(gè)新列表 新列表是被排序的 ss="">print(ll) #[1, 5, 5, 6, 7, 9, 12, 13, 18] ss="alt"> ss="">ss="attribute">l2 = ss="attribute-value">sorted(lst,ss="attribute">reverse=ss="attribute-value">True) #倒序 ss="alt">print(l2) #[18, 13, 12, 9, 7, 6, 5, 5, 1]
ss="dp-xml">ss="alt">#根據(jù)字符串長(zhǎng)度給列表排序 ss="">ss="attribute">lst = ['one', 'two', 'three', 'four', 'five', 'six'] ss="alt">def f(s): ss=""> return len(s) ss="alt">ss="attribute">l1 = ss="attribute-value">sorted(lst, ss="attribute">key=ss="attribute-value">f, ) ss="">print(l1) #['one', 'two', 'six', 'four', 'five', 'three']
- enumerate() 獲取集合的枚舉對(duì)象
ss="dp-xml">ss="alt">ss="attribute">lst = ['one','two','three','four','five'] ss="">for index, el in enumerate(lst,1): # 把索引和元素一起獲取,索引默認(rèn)從0開始. 可以更改 ss="alt"> print(index) ss=""> print(el) ss="alt"># 1 ss=""># one ss="alt"># 2 ss=""># two ss="alt"># 3 ss=""># three ss="alt"># 4 ss=""># four ss="alt"># 5 ss=""># five
- all() 可迭代對(duì)象中全部是True, 結(jié)果才是True
- any() 可迭代對(duì)象中有一個(gè)是True, 結(jié)果就是True
ss="dp-xml">ss="alt">print(all([1,'hello',True,9])) #True ss="">print(any([0,0,0,False,1,'good'])) #True
- zip() 函數(shù)用于將可迭代的對(duì)象作為參數(shù), 將對(duì)象中對(duì)應(yīng)的元素打包成一個(gè)元組, 然后返回由這些元組組成的列表. 如果各個(gè)迭代器的元素個(gè)數(shù)不一致, 則返回列表長(zhǎng)度與最短的對(duì)象相同
ss="dp-xml">ss="alt">ss="attribute">lst1 = [1, 2, 3, 4, 5, 6] ss="">ss="attribute">lst2 = ['醉鄉(xiāng)民謠', '驢得水', '放牛班的春天', '美麗人生', '辯護(hù)人', '被嫌棄的松子的一生'] ss="alt">ss="attribute">lst3 = ['美國', '中國', '法國', '意大利', '韓國', '日本'] ss="">print(zip(lst1, lst1, lst3)) #ss="tag"><ss="tag-name">zip object at 0x00000256CA6C7A88ss="tag">> ss="alt">for el in zip(lst1, lst2, lst3): ss=""> print(el) ss="alt"># (1, '醉鄉(xiāng)民謠', '美國') ss=""># (2, '驢得水', '中國') ss="alt"># (3, '放牛班的春天', '法國') ss=""># (4, '美麗人生', '意大利') ss="alt"># (5, '辯護(hù)人', '韓國') ss=""># (6, '被嫌棄的松子的一生', '日本')
- fiter() 過濾 (lamda)
b. 語法：fiter(function. Iterable)
function: 用來篩選的函數(shù). 在?lter中會(huì)自動(dòng)的把iterable中的元素傳遞給function. 然后根據(jù)function返回的True或者False來判斷是否保留留此項(xiàng)數(shù)據(jù) , Iterable: 可迭代對(duì)象
ss="dp-xml">ss="alt">def func(i): # 判斷奇數(shù) ss=""> return i % ss="attribute">2 == 1 ss="alt"> ss="attribute">lst = [1,2,3,4,5,6,7,8,9] ss="">ss="attribute">l1 = ss="attribute-value">filter(func, lst) #l1是迭代器 ss="alt">print(l1) #ss="tag"><ss="tag-name">filter object at 0x000001CE3CA98AC8ss="tag">> ss="">print(list(l1)) #[1, 3, 5, 7, 9]
map() 會(huì)根據(jù)提供的函數(shù)對(duì)指定序列列做映射(lamda)
c. 語法：map(function, iterable)
可以對(duì)可迭代對(duì)象中的每一個(gè)元素進(jìn)行映射. 分別去執(zhí)行 function
ss="dp-xml">ss="alt">def f(i): return i ss="">ss="attribute">lst = [1,2,3,4,5,6,7,] ss="alt">ss="attribute">it = ss="attribute-value">map(f, lst) # 把可迭代對(duì)象中的每一個(gè)元素傳遞給前面的函數(shù)進(jìn)行處理. 處理的結(jié)果會(huì)返回成迭代器print(list(it)) #[1, 2, 3, 4, 5, 6, 7]
3. 和作用域相關(guān)
- locals() 返回當(dāng)前作用域中的名字
- globals() 返回全局作用域中的名字
ss="dp-xml">ss="alt">def func(): ss=""> ss="attribute">a = ss="attribute-value">10 ss="alt"> print(locals()) # 當(dāng)前作用域中的內(nèi)容 ss=""> print(globals()) # 全局作用域中的內(nèi)容 ss="alt"> print("今天內(nèi)容很多") ss="">func() ss="alt"># {'a': 10} ss=""># {'__name__': '__main__', '__doc__': None, '__package__': None, '__loader__': ss="alt"># ss="tag"><ss="tag-name">_frozen_importlib_external.SourceFileLoader object at 0x0000026F8D566080ss="tag">>, ss=""># '__spec__': None, '__annotations__': {}, '__builtins__': ss="tag"><ss="tag-name">module 'builtins' ss="alt"># (built-in)ss="tag">>, '__file__': 'D:/pycharm/練習(xí)/week03/new14.py', '__cached__': None, ss=""># 'func': ss="tag"><ss="tag-name">function func at 0x0000026F8D6B97B8ss="tag">>} ss="alt"># 今天內(nèi)容很多
4. 和迭代器/生成器相關(guān)
- range() 生成數(shù)據(jù)
- next() 迭代器向下執(zhí)行一次, 內(nèi)部實(shí)際使?用了__ next__()?方法返回迭代器的下一個(gè)項(xiàng)目
- iter() 獲取迭代器, 內(nèi)部實(shí)際使用的是__ iter__()?方法來獲取迭代器
ss="dp-xml">ss="alt">for i in range(15,-1,-5): ss=""> print(i) ss="alt"># 15 ss=""># 10 ss="alt"># 5 ss=""># 0 ss="alt">ss="attribute">lst = [1,2,3,4,5] ss="">ss="attribute">it = ss="attribute-value">iter(lst) # __iter__()獲得迭代器 ss="alt">print(it.__next__()) #1 ss="">print(next(it)) #2 __next__() ss="alt">print(next(it)) #3 ss="">print(next(it)) #4
5. 字符串類型代碼的執(zhí)行
- eval() 執(zhí)行字符串類型的代碼. 并返回最終結(jié)果
- exec() 執(zhí)行字符串類型的代碼
- compile() 將字符串類型的代碼編碼. 代碼對(duì)象能夠通過exec語句來執(zhí)行或者eval()進(jìn)行求值
ss="dp-xml">ss="alt">ss="attribute">s1 = ss="attribute-value">input("請(qǐng)輸入a+b:") #輸入:8+9 ss="">print(eval(s1)) # 17 可以動(dòng)態(tài)的執(zhí)行代碼. 代碼必須有返回值 ss="alt">ss="attribute">s2 = ss="attribute-value">"for i in range(5): print(i)" ss="">ss="attribute">a = ss="attribute-value">exec(s2) # exec 執(zhí)行代碼不返回任何內(nèi)容 ss="alt"> ss=""># 0 ss="alt"># 1 ss=""># 2 ss="alt"># 3 ss=""># 4 ss="alt">print(a) #None ss=""> ss="alt"># 動(dòng)態(tài)執(zhí)行代碼 ss="">exec(""" ss="alt">def func(): ss=""> print(" 我是周杰倫") ss="alt">""" ) ss="">func() #我是周杰倫
ss="dp-xml">ss="alt">ss="attribute">code1 = ss="attribute-value">"for i in range(3): print(i)" ss="">ss="attribute">com = ss="attribute-value">compile(code1, "", ss="attribute">mode=ss="attribute-value">"exec") # compile并不會(huì)執(zhí)行你的代碼.只是編譯 ss="alt">exec(com) # 執(zhí)行編譯的結(jié)果 ss=""># 0 ss="alt"># 1 ss=""># 2 ss="alt"> ss="">ss="attribute">code2 = ss="attribute-value">"5+6+7" ss="alt">ss="attribute">com2 = ss="attribute-value">compile(code2, "", ss="attribute">mode=ss="attribute-value">"eval") ss="">print(eval(com2)) # 18 ss="alt"> ss="">ss="attribute">code3 = ss="attribute-value">"name = input('請(qǐng)輸入你的名字:')" #輸入:hello ss="alt">ss="attribute">com3 = ss="attribute-value">compile(code3, "", ss="attribute">mode=ss="attribute-value">"single") ss="">exec(com3) ss="alt">print(name) #hello
6. 輸入輸出
- print() : 打印輸出
- input() : 獲取用戶輸出的內(nèi)容
ss="dp-xml">ss="alt">print("hello", "world", ss="attribute">sep=ss="attribute-value">"*", ss="attribute">end=ss="attribute-value">"@") # sep:打印出的內(nèi)容用什么連接,end:以什么為結(jié)尾 ss="">#hello*world@
7. 內(nèi)存相關(guān)
hash() : 獲取到對(duì)象的哈希值(int, str, bool, tuple). hash算法:(1) 目的是唯一性 (2) dict 查找效率非常高, hash表.用空間換的時(shí)間 比較耗費(fèi)內(nèi)存
ss="dp-xml">ss="alt">ss="attribute">s = ss="attribute-value">'alex' ss="">print(hash(s)) #-168324845050430382 ss="alt"> ss=""> ss="alt">ss="attribute">lst = [1, 2, 3, 4, 5] ss="">print(hash(lst)) #報(bào)錯(cuò),列表是不可哈希的 ss="alt">id() : 獲取到對(duì)象的內(nèi)存地址 ss=""> ss="alt"> ss="">ss="attribute">s = ss="attribute-value">'alex' ss="alt">print(id(s)) #2278345368944
8. 文件操作相關(guān)
open() : 用于打開一個(gè)文件, 創(chuàng)建一個(gè)文件句柄
ss="dp-xml">ss="alt">ss="attribute">f = ss="attribute-value">open('file',ss="attribute">mode=ss="attribute-value">'r',ss="attribute">encoding=ss="attribute-value">'utf-8') ss="">f.read() ss="alt">f.close()
9. 模塊相關(guān)
__ import__() : 用于動(dòng)態(tài)加載類和函數(shù)
ss="dp-xml">ss="alt"># 讓用戶輸入一個(gè)要導(dǎo)入的模塊 ss="">import os ss="alt">ss="attribute">name = ss="attribute-value">input("請(qǐng)輸入你要導(dǎo)入的模塊:") ss="">__import__(name) # 可以動(dòng)態(tài)導(dǎo)入模塊
10. 幫 助
help() : 函數(shù)用于查看函數(shù)或模塊用途的詳細(xì)說明
ss="dp-xml">ss="alt">print(help(str)) #查看字符串的用途
11. 調(diào)用相關(guān)
callable() : 用于檢查一個(gè)對(duì)象是否是可調(diào)用的. 如果返回True, object有可能調(diào)用失敗, 但如果返回False. 那調(diào)用絕對(duì)不會(huì)成功
ss="dp-xml">ss="alt">ss="attribute">a = ss="attribute-value">10 ss="">print(callable(a)) #False 變量a不能被調(diào)用 ss="alt"># ss="">def f(): ss="alt"> print("hello") ss=""> print(callable(f)) # True 函數(shù)是可以被調(diào)用的
12. 查看內(nèi)置屬性
dir() : 查看對(duì)象的內(nèi)置屬性, 訪問的是對(duì)象中的__dir__()方法
ss="dp-xml">ss="alt">print(dir(tuple)) #查看元組的方法
