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1.系統(tǒng)自帶的函數(shù)： >>> dir(__builtins__) ['ArithmeticError', 'AssertionError', 'AttributeError', 'BaseException', 'BlockingIOError', 'BrokenPipeError', 'BufferError', 'BytesWarning', 'ChildProcessError', 'ConnectionAbortedError', 'ConnectionError', 'ConnectionRefusedError', 'ConnectionResetError', 'DeprecationWarning', 'EOFError', 'Ellipsis', 'EnvironmentError', 'Exception', 'False', 'FileExistsError', 'FileNotFoundError', 'FloatingPointError', 'FutureWarning', 'GeneratorExit', 'IOError', 'ImportError', 'ImportWarning', 'IndentationError', 'IndexError', 'InterruptedError', 'IsADirectoryError', 'KeyError', 'KeyboardInterrupt', 'LookupError', 'MemoryError', 'ModuleNotFoundError', 'NameError', 'None', 'NotADirectoryError', 'NotImplemented', 'NotImplementedError', 'OSError', 'OverflowError', 'PendingDeprecationWarning', 'PermissionError', 'ProcessLookupError', 'RecursionError', 'ReferenceError', 'ResourceWarning', 'RuntimeError', 'RuntimeWarning', 'StopAsyncIteration', 'StopIteration', 'SyntaxError', 'SyntaxWarning', 'SystemError', 'SystemExit', 'TabError', 'TimeoutError', 'True', 'TypeError', 'UnboundLocalError', 'UnicodeDecodeError', 'UnicodeEncodeError', 'UnicodeError', 'UnicodeTranslateError', 'UnicodeWarning', 'UserWarning', 'ValueError', 'Warning', 'WindowsError', 'ZeroDivisionError', '__build_class__', '__debug__', '__doc__', '__import__', '__loader__', '__name__', '__package__', '__spec__', 'abs', 'all', 'any', 'ascii', 'bin', 'bool', 'bytearray', 'bytes', 'callable', 'chr', 'classmethod', 'compile', 'complex', 'copyright', 'credits', 'delattr', 'dict', 'dir', 'divmod', 'enumerate', 'eval', 'exec', 'exit', 'filter', 'float', 'format', 'frozenset', 'getattr', 'globals', 'hasattr', 'hash', 'help', 'hex', 'id', 'input', 'int', 'isinstance', 'issubclass', 'iter', 'len', 'license', 'list', 'locals', 'map', 'max', 'memoryview', 'min', 'next', 'object', 'oct', 'open', 'ord', 'pow', 'print', 'property', 'quit', 'range', 'repr', 'reversed', 'round', 'set', 'setattr', 'slice', 'sorted', 'staticmethod', 'str', 'sum', 'super', 'tuple', 'type', 'vars', 'zip'] ? 2.定義一個(gè)函數(shù) >>> def a2_333():???????????? #def定義一個(gè)函數(shù)，a2_333函數(shù)名，字母開頭 ...???? pass???????????????? ?#()中的參數(shù)可有可無(wú) ... ? >>> a2_333????????????????? #未調(diào)用函數(shù)，只是打印了一下函數(shù)名 <function a2_333 at 0x0000019CF2431EA0>???? ?#function代表該名字是函數(shù) ??????????????????????????????????????????? #at代表了該函數(shù)在內(nèi)存中的地址 >>> a2_333()???????????????? #函數(shù)名后加()，便可調(diào)用該函數(shù) >>>? ? >>> def count_letter(s):??????? #函數(shù)名不要與系統(tǒng)自帶的函數(shù)名、定義的變量名沖突， ...???? result=0?????????????? #s為參數(shù)，在括號(hào)中可以寫多個(gè)參數(shù)，無(wú)限制 ...???? for i in s: ...???????? if i >="a" and i <="z": ...???????????? result=result 1 ...???? return result??????????? #函數(shù)執(zhí)行完畢后，一定要有個(gè)返回值 ... >>> count_letter("a1b2Z3") 2 ? >>> count_letter("skdjhf3ksdhf")?? #函數(shù)定義好后，傳不同的參數(shù)，均能正確輸出 11??????????????????????????? ?#封裝的概念，調(diào)用時(shí)不用關(guān)注內(nèi)部的邏輯 ? >>>count_letter()??????????????? #調(diào)用的時(shí)候，傳參一個(gè)都不能少，除非函數(shù)使用默認(rèn) Traceback (most recent call last):?? ?#參數(shù) ? File "<stdin>", line 1, in <module> TypeError: count_letter() missing 1 required positional argument: 's' ? >>> def count_digit(s): ...???? result=0 ...???? for i in s: ...???????? if i>="0" and i<="9": ...???????????? result =1 ...?????????????????????????? ?????????#該函數(shù)就沒有返回值 ... >>> print(count_digit("sadhfasjdgsjf"))???? #沒有return的函數(shù)，默認(rèn)返回None None >>> print(count_digit("ssjhd24")) ????????#沒有return的函數(shù)，默認(rèn)返回None None ? >>> def count_digit(s): ...???? result=0 ...???? for i in s: ...???????? if i>="0" and i<="9": ...???????????? result =1 ...???? return???????????????????????? #有return,但是后面沒有寫任何參數(shù)?? ... >>> print(count_digit("sadhfasjdgsjf"))? ?#依然返回None None >>> print(count_digit("ssjhd24")) None ? >>> print(None)?????????????????????? #單獨(dú)打印None，還是會(huì)有結(jié)果輸出 None ? >>> print(none)????????????????????? ?#打印小寫none，提示未定義 Traceback (most recent call last): ? File "<stdin>", line 1, in <module> NameError: name 'none' is not defined ? ? 3.函數(shù)的建壯性 輸入兩個(gè)數(shù)，返回相加的結(jié)果： def add(a,b): ??? return(a b) ? print(add(1,2)) ?????????????#在文件中執(zhí)行時(shí)，一定要加print,否則無(wú)輸出結(jié)果 ? >>> add(1,2)?????????????? #終端模式時(shí)，不必加print便有正確輸出 3 該代碼存在安全隱患，如果a,b類型不一致，會(huì)報(bào)錯(cuò) >>> def add(a,b): ...???? return(a b) ... >>> add(1,"2")???????????? #傳入的a,b的類型不一致 Traceback (most recent call last): ? File "<stdin>", line 1, in <module> ? File "<stdin>", line 2, in add TypeError: unsupported operand type(s) for : 'int' and 'str' ? 改進(jìn)后的代碼是： def add(a,b): ? ??if isinstance(a,(int,float,complex)) and isinstance(b,(int,float,complex)): #判斷a,b是否都 ??????? return(a b)???????????????????????????????????????????? #是int類型 ??? print("Adding different types of objects is not supported")????? ?#return具有短路功能 ??? return None print(add(1,"2")) 執(zhí)行結(jié)果： E:\>python a.py Adding different types of objects is not supported None ? ? 4.函數(shù)的作用域 >>> n=1??????????????????? #全局變量 >>> def func(): ...???? n=2????????????????? #在函數(shù)內(nèi)部定義的變量叫做局部變量，函數(shù)體內(nèi)部有效 ...???? return n ... >>> print(func())??????????? ?#返回函數(shù)內(nèi)的n值 2 >>> print(n)???????????????? #返回全局變量n的值 1 ? ? >>> def func(): ...???? n=2?????????????????? #只存在一個(gè)局部變量n，不存在全局變量n ...???? return n ... >>> print(func()) 2 >>> print(n)????????????????? #不存在全局變量n,提示n未定義 Traceback (most recent call last): ? File "<stdin>", line 1, in <module> NameError: name 'n' is not defined ? ? n=1????????????????????????? #全局變量中有n def func(): ??? return n 1??????????????? #函數(shù)中使用了n，但是在函數(shù)中未定義，會(huì)現(xiàn)在函數(shù)體內(nèi) ??????????????????????????? #部找n，如果找不到，就到函數(shù)外面找 print(func()) 運(yùn)行結(jié)果： E:\>python a.py 2??????????????????????????? ?#依然能返回正確的結(jié)果 ? ? n=1???????????????????????? ?#n是全局變量 def func(): ??? n =1???????????????????? #n在函數(shù)中還未賦值，就加1 ??? return n print(func()) print(n) 運(yùn)行結(jié)果： E:\>python a.py Traceback (most recent call last): ? File "a.py", line 6, in <module> ??? print(func()) ? File "a.py", line 3, in func ??? n =1 UnboundLocalError: local variable 'n' referenced before assignment 局部變量n在賦值前被引用了，意思就是還未賦值 ? 解決方法：在函數(shù)內(nèi)部也先賦一下值 n=1 def func(): ??? n=10 ??? n =1 ??? return n print(func()) print(n) 運(yùn)行結(jié)果： E:\>python a.py 11 1 ? 解決方法：使用全局變量的n n=1 def func(): ??? global n????????????? #函數(shù)內(nèi)部，也使用全局變量的n ??? n =1??????????????? #函數(shù)內(nèi)部n 1,同時(shí)全局變量的n也加了1 ??? return n print(func()) print(n) 運(yùn)行結(jié)果： E:\>python a.py????????? ?#n為2 2?????????????????????? #此方法不推薦 2 ? n=1 def func(a): ??? a =1 ??? return a print(func(n))???????????? #傳的參數(shù)為n，n在程序中是全局變量1，所以a=2 print(n)????????????????? #此方法比較推薦使用 運(yùn)行結(jié)果： E:\>python a.py 2 1 ? ? n=[]??????????????????? ?#n在全局變量的位置，但是是列表，列表是可變對(duì)象 def func(a): ??? a.append(1) ??? return a print(func(n)) print(n) 運(yùn)行結(jié)果： E:\>python a.py [1] [1] ? ? n={} def func(a): ??? a[1]=1 ??? return a print(func(n)) print(n) 運(yùn)行結(jié)果; E:\>python a.py {1: 1} {1: 1} ? ? n="abc" def func(a): ??? a=a "d" ??? return a print(func(n)) print(n) 運(yùn)行結(jié)果： E:\>python a.py abcd abc 原則1： 如果你傳入的參數(shù)是變量a,這個(gè)變量是可變類型(list,dict,set) 那么函數(shù)內(nèi)部對(duì)于這個(gè)參數(shù)的所有操作結(jié)果都會(huì)影響外部的參數(shù)值 原則2： 如果你傳入的參數(shù)是個(gè)變量a，這個(gè)變量是不可變類型（字符串，整數(shù)，小數(shù)，元祖） 那么函數(shù)內(nèi)部對(duì)于這個(gè)參數(shù)的所有操作結(jié)果都不會(huì)影響外部的參數(shù)值 ? ? >>> def func(): ...???? n=2 ...???? return n ... >>> func=1???????????????? #func是一個(gè)函數(shù)的名字，賦值后，從函數(shù)變成了int >>> func()????????????????? #整數(shù)加(),打印時(shí)提示不可調(diào)用 Traceback (most recent call last): ? File "<stdin>", line 1, in <module> TypeError: 'int' object is not callable ? >>> del func??????????????? #非內(nèi)置的函數(shù)，提示不可調(diào)用后，可刪除后再次定義 >>> def func(): ...???? n=2 ...???? return n ... >>> print(func())???????????? #函數(shù)功能正常 2 ? ? >>> del func()?????????????? #當(dāng)刪除函數(shù)時(shí)，不要加(),否則會(huì)報(bào)錯(cuò)兒 ? File "<stdin>", line 1 SyntaxError: can't delete function call ? ? >>> print(len("abc"))????????? #len函數(shù)是系統(tǒng)自帶的函數(shù) 3 >>> len=10?????????? >>> print(len)????????????? ?#len變成了10 10 >>> print(len("abc"))???????? #此時(shí)在調(diào)用函數(shù)，提示int類型不可調(diào)用 Traceback (most recent call last): ? File "<stdin>", line 1, in <module> TypeError: 'int' object is not callable >>> del len?????????????????? #刪除掉len >>> print(len("abc"))?????????? #len為系統(tǒng)自帶函數(shù)，刪除后未經(jīng)再次定義依然可以調(diào)用 3 ? ? 5.調(diào)用時(shí)參數(shù) 1)?????? 必填參數(shù) >>> def add(a,b):??????????? ?#函數(shù)定義了兩個(gè)參數(shù)a,b ...???? return(a b) ... >>> print(add(1))???????????? #調(diào)用時(shí)只傳入了一個(gè)參數(shù) Traceback (most recent call last): ? File "<stdin>", line 1, in <module> TypeError: add() missing 1 required positional argument: 'b'?????? #報(bào)錯(cuò)，少參數(shù) ? 2)?????? 可選參數(shù) >>> def add(a,b=100):??????? #定義了兩個(gè)參數(shù)a,b，b的默認(rèn)值是100 ...???? return(a b) ... >>> print(add(1))???????????? #雖然只傳入了一個(gè)參數(shù)，但是能正確輸出結(jié)果，原因在于 101??????????????????????? ?#b使用的是默認(rèn)參數(shù)值 默認(rèn)值是在定義時(shí)就設(shè)定的。 ? ? >>> def add(a,b=100):??????? #參數(shù)b的默認(rèn)值是100 ...???? return(a b) ... >>> print(add(1,10))???????? #傳入的b值是10 11??????????????????????? ?#最后打印使用的是傳入的值，非默認(rèn)值 ? ? >>> def add(a,b=100): ...???? return(a b) ... >>> print(add(b=1,a=10))?? #調(diào)用時(shí)，參數(shù)賦值，也可正確輸出 11 ? ? >>> def add(a,b=100):?????? #a是必填參數(shù)，b是可選參數(shù) ...???? return a b ... >>> print(add(b=1))???????? #傳參時(shí)，必填參數(shù)無(wú)，會(huì)報(bào)錯(cuò) Traceback (most recent call last): ? File "<stdin>", line 1, in <module> TypeError: add() missing 1 required positional argument: 'a' ? ? >>> def add(a=100,b):?????? #默認(rèn)值參數(shù)后有非默認(rèn)值參數(shù) ...???? return a b?????????? ... ? File "<stdin>", line 1 SyntaxError: non-default argument follows default argument 默認(rèn)值參數(shù)后面跟了非默認(rèn)值參數(shù) 函數(shù)定義時(shí)，默認(rèn)值參數(shù)的后面不能有非默認(rèn)值參數(shù)， ? 3)?????? 可變參數(shù)： def add(a,b,*c): ??? print(type(c)) ??? print(c)?????????????????????? ?#可變參數(shù)不需要對(duì)應(yīng)，便可正確輸出 ??? return a,b,c print(add(1,2,3,4,5)) 運(yùn)行結(jié)果： E:\>python a.py <class 'tuple'>??????????????????? ?#c的類型是元祖 (3, 4, 5)????????????????????????? ?#c的值是(3,4,5) (1, 2, (3, 4, 5))????????????????????? #a的值是1，b的值是2 ? ? def add(a,b,**c):??????????????? #c前面有兩個(gè)* ??? print(type(c)) ??? print(c) ? print(add(1,2,c=3,d=4,e=5)) 運(yùn)行結(jié)果： E:\>python a.py <class 'dict'>????????????????? #c的類型是dict {'c': 3, 'd': 4, 'e': 5}???????????? ?#c的值是賦值的結(jié)果，c,d,e是key,3,4,5,是value None ? ? >>> def add(a,b,*c): ...???? print(type(c)) ...???? print(c) ...???? return a,b,c ... >>> print(add(1,2,3,4,5)) <class 'tuple'> (3, 4, 5) (1, 2, (3, 4, 5)) >>> print(a)??????????????????????????? #a為非可變參數(shù)，未對(duì)應(yīng)賦值，便提示未定義 Traceback (most recent call last): ? File "<stdin>", line 1, in <module> NameError: name 'a' is not defined ? ? def add(a,b,*c): ??? print(type(c)) ??? print(c) ??? return a,b,c a,b,*c=add(1,2,3,4,5)??????????????????? #a，b非可變參數(shù)賦值后，可正常打印 print(add(1,2,3,4,5)) print(a) print(b) 運(yùn)行結(jié)果： E:\>python a.py <class 'tuple'> (3, 4, 5) <class 'tuple'> (3, 4, 5) (1, 2, (3, 4, 5)) 1 2 ? ? 6.返回時(shí)多個(gè)參數(shù) def time_ten_bigger(a,b): ??? return a*10,b*10 print(time_ten_bigger(1,10))?? print(a) print(b)?????? 運(yùn)行結(jié)果： E:\>python a.py (10, 100)?????????????????????? #返回了函數(shù)調(diào)用的結(jié)果 Traceback (most recent call last): ? File "a.py", line 5, in <module> ??? print(a) NameError: name 'a' is not defined#print(a)提示a未定義 ? 正確的代碼是： def time_ten_bigger(a,b): ??? return a*10,b*10????????? ?#返回兩個(gè)值，實(shí)際自動(dòng)的將兩個(gè)值放在了元祖里 a,b=time_ten_bigger(1,10)?????? #將a,b分別與函數(shù)的參數(shù)對(duì)應(yīng) print(time_ten_bigger(1,10))?? print(a) print(b) 運(yùn)行結(jié)果： E:\>python a.py (10, 100)?????????????????????? #函數(shù)返回的值 10??????????????????????????? ?#a的值 100??????????????????????????? #b的值 ? def time_ten_bigger(a,b):????????? ??? return a*10,b*10???????????? #函數(shù)返回值參數(shù)都乘以10 a,b=time_ten_bigger(1,10)???????? #a是1的十倍，b是10的十倍 print(time_ten_bigger(b=1,a=10))?? #這個(gè)函數(shù)定義的參數(shù)前后位置不一樣 print(a) print(b)???? 運(yùn)行結(jié)果： E:\>python a.py (100, 10) 10 100??? ? 小練習(xí): 1.統(tǒng)計(jì)一句話中有多少個(gè)數(shù)字 >>> def count_digit(s): ...???? result=0 ...???? for i in s: ...???????? if i>="0" and i<="9": ...???????????? result =1 ...???? return result?????????????? ... >>> count_digit("sadhfasjdgsjf") 0 >>> count_digit("ssjhd24") 2 ? ? 2.使用可變參數(shù)的方式求1-5的和 def add(a,b,*c):????????????????? #c是個(gè)元祖，使用遍歷的方法 ??? result=0 ??? for i in c: ??????? result =i ??? return result a b print(add(1,2,3,4,5)) 運(yùn)行結(jié)果： E:\>python a.py 15 ? ? 3.使用可變參數(shù)，求add(1,2,c=3,d=4,e=5)所有數(shù)的和 def add(a,b,**c):???????????????? ?#c是字典，遍歷字典的values值 ??? result=0???????????????????? #方法1： ??? for i in c.values():????????????????? ??????? result =i ??? return a b result print(add(1,2,c=3,d=4,e=5)) 運(yùn)行結(jié)果： E:\>python a.py 15 ? def add(*a,**c):??????????????? #方法2：字典 元祖 ??? result=0? ? ??for i in a: ??????? result =i?????????? ??? for i in c.values():????????????????? ??????? result =i ??? return result print(add(1,2,c=3,d=4,e=5)) 運(yùn)行結(jié)果： E:\>python a.py 15 ? ? 4.使用可變參數(shù)，求add(1,2,3,4,c=5,d=6,e=7)的和 def add(a,b,*c,**d): ??? result=a b ??? for i in d.values(): ??????? result =i ??? for i in c: ??????? result =i ??? return result print(add(1,2,3,4,c=5,d=6,e=7)) 運(yùn)行結(jié)果： E:\>python a.py 28 ? 來(lái)源：http://www./content-1-112451.html |
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