python3与JS有什么不同

0.注释与代码块

JavaScript:
//单行注释/* * 多行 * 注释 */
python:
#单行注释'''多行注释'''

行和缩进

学习Python与其他语言最大的区别就是，Python的代码块不使用大括号（{}）来控制类，函数以及其他逻辑判断。python最具特色的就是用缩进来写模块。

1.变量

变量声明与赋值

JavaScript:
//变量声明赋值var a = "变量a";var A = "变量A";console.log(a);console.log(A);//多个变量赋值var a = "变量a",    A = "变量A";console.log(a, A);
python:
#变量声明赋值a = "变量a";A = "变量A";print(a);print(A);#多个变量赋值a,A = "变量a", "变量A";print(a, A);

变量交换

JavaScript:
var b = 1,    c = 2;console.log(b, c);[b, c] = [c, b]console.log(b, c);
python:
b,c=1,2print(b,c);b,c=c,bprint(b,c);

常用变量类型

JavaScript:
//typeof(??)<--用来查看类型console.log(typeof(1))console.log(typeof(1.0))console.log(typeof('a'))console.log(typeof('aaaa'))console.log(typeof([]))console.log(typeof({}))
python:
#type(??)<--用来查看类型print(type(1))print(type(1.0))print(type('a'))print(type('aaaa'))print(type([]))print(type({}))

常用变量类型转换

JavaScript:
console.log(typeof((1).toString()), "转为字符串类型")console.log(typeof(parseInt("123")), "转为数字类型")console.log(typeof(Number("123")), "转为数字类型")console.log(typeof(parseFloat("123")), "转为带小数点的数字类型")
python:
print(type( str(1) ),"转为字符串类型")print(type( int("123") ),"转为数字类型")print(type( float("123") ),"转为浮点类型")

删除变量

JavaScript:
var d = "aaa"console.log(d)delete d
python:
d="aaa"print(d)del d

2.字符串

字符串截取

JavaScript:
//"xxx".substring(开始索引,结束索引但不包括 结束索引 处的字符)//"xxx".substring(开始索引,截取长度)var e = "0123456abcdef"console.log("完整截取:", e.substring(0, e.length));console.log("完整截取:", e.substr(0, e.length));console.log("截取012:", e.substring(0, 3));console.log("截取012:", e.substr(0, 3));console.log("截取索引为10值:", e[10]);
python:
e="0123456abcdef"print("完整截取:",e[:-1])print("截取012:",e[0:3])print("截取索引为10值:",e[10])

字符串更新

JavaScript:
console.log("更新字符串 :", e.substr(0, 6) + 'hahahhaha!')
python:
print("更新字符串 :", e[:6] + 'hahahhaha!')

英文大小写转换

JavaScript:
console.log("转大写:", e.toUpperCase());console.log("转小写:", e.toLowerCase());
python:
print("转大写:",e.upper())print("转小写:",e.lower())

判断是否存在字符

JavaScript:
console.log("正确输出:", e.indexOf("a"))console.log("错误输出:", e.indexOf("A"))
python:
print("正确输出:","a" in e)print("错误输出:","A" in e)

输出指定重复数

JavaScript:
console.log("10输出:", new Array(10 + 1).join(e)) //通过将空数组拼接时中间插入字符串
python:
print("10输出:",e*10)

换行输出

JavaScript:

console.log("第一行\n" + 
"第二行\n" + "第三行\n");

python:

print('''第一行
第二行
第三行''');

切割字符串

JavaScript:
console.log(e.split(''))console.log(e.split('a'))
python:
print(list(e))print(e.split('a'))

4.循环遍历

输出0~99的整数

JavaScript:
for (var o = 0; o < 100; o++) {    console.log(o)}
python:
for i in range(0,100):    print(i)

数组遍历

JavaScript:

var f = ["0", "1", "2", "3", "4", "5", "6", "a", "b", "c", "d", "e", "f"];for (i in f) {    console.log("值:" + f[i], "索引" + i);}//或使用:f.forEach(function(v, i) {    console.log("值:" + v, "索引" + i);});
python:
#普通遍历f=["0", "1", "2", "3", "4", "5", "6", "a", "b", "c", "d", "e", "f"]for i in f:    print(i)#含索引for i,v in enumerate(f):    print("值:"+v,"索引"+str(i))#或含索引for i in range(0,len(f)):    print("值:" + f[i], "索引" + i)

5.函数

JavaScript:

//空函数function g0() {}//带参数与返回值function g1(v1, v2, v3 = "默认值") {    return 1;}//带参数与返回值或g2 = function(v1, v2, v3 = "默认值") {    return 2;}//多返回值function g3(v1, v2, v3 = "默认值") {    return [1, 2];}
python:
#空函数def g0():pass#带参数与返回值def g1(v1,v2,v3="默认值"):    return 1#多返回值def g3(v1,v2,v3="默认值"):    return 1,2

6.集合

JavaScript:
arr=[1,2,3,1,1,1,"ccc","effd","ccc"]//去除重复//略.....//数组拼接var c=arr.concat([9,10,11] );//获取长度console.log(c.length);//判断是否存在console.log(c.indexOf(3));//追加元素c.push("元素");
python
arr=[1,2,3,1,1,1,"ccc","effd","ccc"]#去除重复 print(list(set(arr)) )#数组拼接c=ar+[9,10,11] ;#获取长度print(len(c))#判断是否存在print(3 in c)#追加元素c.append("元素");

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