本文只是粗略比较python3与JavaScript的一些基本编程中语法不相同的地方
如果你想深入了解推荐阅读其官方文档或其他网站更加详细的教程

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=1,2
print(b,c);
b,c=c,b
print(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");