この記事では、Python の変数と演算子に関するコード例を紹介します。一定の参考値があります。必要な友人は参照できます。お役に立てれば幸いです。
変数とは
数学的演算を実行するために 2 つのリストを想定します
>>> [1,2,3,4,5,6] [1,2,3] Traceback (most recent call last): File "<pyshell#0>", line 1, in <module> [1,2,3,4,5,6] [1,2,3] TypeError: list indices must be integers or slices, not tuple //A B,先把A乘以3,然后加上B,最后再加上列表A >>> [1,2,3,4,5,6]*3+[1,2,3]+[1,2,3,4,5,6] [1, 2, 3, 4, 5, 6, 1, 2, 3, 4, 5, 6, 1, 2, 3, 4, 5, 6, 1, 2, 3, 1, 2, 3, 4, 5, 6] >>> A = [1,2,3,4,5,6] >>> print(A) [1, 2, 3, 4, 5, 6] >>> B = [1,2,3] >>> A*3 + B + A [1, 2, 3, 4, 5, 6, 1, 2, 3, 4, 5, 6, 1, 2, 3, 4, 5, 6, 1, 2, 3, 1, 2, 3, 4, 5, 6]
変数名の命名規則
変数名には文字、数字、アンダースコアのみを使用できます
>>> 1a = 2 //变量名的首字母不能是数字 SyntaxError: invalid syntax >>> A2 = '1' >>> _2 = '1' >>> A*B='1' SyntaxError: can't assign to operator
システム キーワードは変数名に使用できません予約済みキーワード
>>> and = 1 SyntaxError: invalid syntax >>> if = 2 SyntaxError: invalid syntax >>> import = 3 SyntaxError: invalid syntax >>> type = 3 //type不是系统保留关键字,但是不建议作为变量名,否则极易出错 >>> print(type) 3 >>> type = 1 >>> type(1) Traceback (most recent call last): File "<pyshell#1>", line 1, in <module> type(1) TypeError: 'int' object is not callable >>> 1(1) Traceback (most recent call last): File "<pyshell#2>", line 1, in <module> 1(1) TypeError: 'int' object is not callable
Python 動的言語の機能。宣言時には不要です。変数型
>>> a = '1' >>> a = 1 >>> a = (1,2,3) >>> a = {1,2,3}
値型と参照型
int、str、tupleは値型(不変)、list、set、dictは参照型(変更可能)
#1.int>>> a = 1 >>> b = a >>> a = 3 >>> print(b) 12.list
>>> a = [1,2,3,4,5] >>> b = a >>> a[0] = '1' >>> print(a) ['1', 2, 3, 4, 5] >>> print(b) ['1', 2, 3, 4, 5] >>> a = [1,2,3] >>> id(a) 4405825224 >>> hex(id(a)) '0x1069b8ec8' >>> a[0]='1' >>> id(a) 4405825224 >>>3.str
>>> a = 'hello' >>> a = a + 'python' //a加上一个新的字符串,不再是原来的字符串了 >>> print(a) hellopython >>> b = 'hello' >>> id(b) 4405534032 >>> b = b + 'python' //加上新的字符串后,id改变 >>> id(b) 4355329456 >>> 'python'[0] 'p' >>> 'python'[0]='o' Traceback (most recent call last): File "<pyshell#8>", line 1, in <module> 'python'[0]='o' TypeError: 'str' object does not support item assignment4.tuple
>>> a = (1,2,3) >>> a[0] = '1' Traceback (most recent call last): File "<pyshell#21>", line 1, in <module> a[0] = '1' TypeError: 'tuple' object does not support item assignment >>> b = [1,2,3] >>> b.append(4) >>> print(b) [1, 2, 3, 4] >>> c = (1,2,3) >>> c.append(4) Traceback (most recent call last): File "<pyshell#26>", line 1, in <module> c.append(4) AttributeError: 'tuple' object has no attribute 'append' >>> a = (1,2,3,[1,2,4]) >>> a[2] 3 >>> a[3] [1, 2, 4] >>> a[3][2] 4 >>> a = (1,2,3,[1,2,['a','b','c']]) >>> a[3][2][1] 'b' >>> a = (1,2,3,[1,2,4]) >>> a[2] = '3' Traceback (most recent call last): File "<pyshell#7>", line 1, in <module> a[2] = '3' TypeError: 'tuple' object does not support item assignment >>> a[3][2] = '4' >>> print(a) //元组内的列表可变 (1, 2, 3, [1, 2, '4'])
Operator
1. 算術演算子: ,-,*,/,//,%,**>>> 'hello'+'world' 'helloworld' >>> [1,2,3]*3 [1, 2, 3, 1, 2, 3, 1, 2, 3] >>> 3-1 2 >>> 3/2 1.5 >>> 3//2 //整除 1 >>> 5%2 //求余 1 >>> 2**2 //求N次方 4 >>> 2**5 322. 代入演算子: =, =,- =, *=、/=、%=、**=、//=
>>> c = 1 >>> c = c+1 >>> print(c) 2 >>> c+=1 >>> print(c) 3 >>> c-=1 >>> print(c) 2 >>> c++ //python中没有自增和自减运算符 SyntaxError: invalid syntax >>> c-- SyntaxError: invalid syntax >>> b=2 >>> a=3 >>> b+=a >>> print(b) 5 >>> b-=a >>> print(b) 2 >>> b*=a >>> print(b) 63. 比較 (関係) 演算子: ==、! =、>、<、>=、<=
>>> 1==1 True >>> 1>1 False >>> 1>=1 True >>> a>=b Traceback (most recent call last): File "<pyshell#3>", line 1, in <module> a>=b NameError: name 'a' is not defined >>> a=1 >>> b=2 >>> a!=b True >>> b=1 >>> b+=b>=1 //b=b+True >>> print(b) 2 >>> print(b>=1) True >>> 1>1 False >>> 2>3 False >>> 'a'>'b' False >>> ord('a') 97 >>> ord('b') 98 >>> 'abc'<'abd' //实际上是a和a比,b和b比,c和d比 True >>> ord('abc') Traceback (most recent call last): File "<pyshell#12>", line 1, in <module> ord('abc') TypeError: ord() expected a character, but string of length 3 found >>> ord('c') 99 >>> ord('d') 100 >>> [1,2,3]<[2,3,4] True >>> (1,2,3)<(1,3,2) True4. 論理演算子: and、or、not
>>> True and True True >>> True and False False >>> True or False True >>> False or False False >>> not False True >>> not True False >>> not not True True0 は False とみなされ、0 以外は True を意味します <p></p> <pre class="brush:php;toolbar:false">>>> 1 and 1 1 >>> 'a' and 'b' 'b' >>> 'a' or 'b' 'a' >>> not 'a' False >>> a = True >>> b = False >>> a or b True >>> b and a False空の文字列 False
>>> not 0.1 False >>> not '' True >>> not '0' False空のリスト False
>>> not [] True >>> not [1,2] False >>> [1] or [] [1] >>> [] or [1] [1] >>> 'a' and 'b' 'b' >>> '' and 'b' '' >>> 1 and 0 0 >>> 0 and 1 0 >>> 1 and 2 2 >>> 2 and 1 1 >>> 0 or 1 1 >>> 1 or 0 1 >>> 1 or 2 15.メンバー演算子:in、in ではありません
>>> a = 1 >>> a in [1,2,3,4,5] True >>> b = 6 >>> b in [1,2,3,4,5] False >>> b not in [1,2,3,4,5] True >>> b = 'h' >>> b in 'hello' True >>> b not in (1,2,3,4,5) True >>> b not in {1,2,3,4,5} True >>> b = 'a' >>> b in {'c':1} False >>> b = 1 >>> b in {'c':1} False >>> b = 'c' >>> b in {'c':1} //字典里面根据key返回 True6.恒等演算記号:is、 is notオブジェクトの 3 つの特性: ID、値、タイプ。「is」を使用して ID を判断し、「==」を使用して値を判断し、「isinstance」を使用してタイプを判断します
>>> a = 1 >>> b = 1 >>> a is b True >>> a='hello' >>> b='world' >>> a is b False >>> c='hello' >>> a is c True >>> a=1 >>> b=2 >>> a==b False >>> a=1 >>> b=1 >>> a is b True >>> a==b True >>> a=1 >>> b=1.0 >>> a==b True >>> a is b //is不是比较值相等,比较的是两个变量的身份(内存地址)是否相等 False >>> id(a) 4374928384 >>> id(b) 4376239272 >>> a={1,2,3} >>> b={2,1,3} >>> a==b //集合是无序的 True >>> a is b False >>> id(a) 4433997384 >>> id(b) 4433996488 >>> c=(1,2,3) >>> d=(2,1,3) >>> c==d //元组是序列,是有序的 False >>> c is d False >>> a=1 >>> b=2 >>> a==b False >>> a is b False >>> a = 'hello' >>> type(a) == int False >>> type(a) == str True >>> isinstance(a,str) //isinstance是判断变量类型的函数 True >>> isinstance(a,int) False >>> isinstance(a,(int,str,float)) True >>> isinstance(a,(int,float)) False7. ビット単位の演算子: (== 数値を 2 進数として演算 ==)
>>> a = 2 >>> b = 3 >>> a & b 2#変数
##10 進数に変換します |
a |
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2 | ##b | 1 | 1||
##1 |
0 |
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## ビット単位の OR 演算。各 2 進数を比較します。一方が 1 である限り 1 が得られ、両方が 0 の場合は 0 | >>> a = 2 >>> b = 3 >>> a | b 3 |
##a |
1 | 0 | 2||
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b | 1 | 1 | 3 |
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ビット単位 OR | 1 | 1 | #3||
# |
以上がPython の変数と演算子のコード例の詳細内容です。詳細については、PHP 中国語 Web サイトの他の関連記事を参照してください。