本文基于python3.8版本,总结了各种数据类型直接的转换规则和方法.算是比较全了,可以收藏当手册来查. 概述 数据类型转换,指的是通过某种方法,将一个数据由原来的类型转换为另外一个类型.比如,我们将字符串“123”转换为数字123,这就是一种数据类型的转换. Python支持各种标准数据类型之间的转换,但并不是任意数据都可以转换的,所有的转换要符合“常理”,逻辑上应该是成立的.比如,你不应该试图将一个complex类型转换为int,因为python也不知该怎么转换. 数据类型转换支持情况汇总

a = "[[1,2], [3,4], [5,6], [7,8], [9,0]]" b = eval(a) print b [[1, 2], [3, 4], [5, 6], [7, 8], [9, 0]][Finished in 0.2s] a = "{1: 'a', 2: 'b'}" b = eval(a) print b print type(b) {1: 'a', 2: 'b'}<type 'dict'>[Finished in 0.2s] ---

目录 1. Math 对象:数学对象,提供对数据的数学计算.如:获取绝对值.向上取整等.无构造函数,无法被初始化,只提供静态属性和方法. 2. Number 对象 :Js中提供数字的对象.包含整数.浮点数等等.并提供数字的类型转换.小数点截取等方法. 1. Math 对象 1.1 介绍 Math 对象,是数学对象,提供对数据的数学计算,如:获取绝对值.向上取整等.无构造函数,无法被初始化,只提供静态属性和方法. 1.2 构造函数 无 :Math 对象无构造函数,无法被初始化,只提供静态属性和方法

题意:求f(n)=1/1+1/2+1/3+1/4-1/n   (1 ≤ n ≤ 108).,精确到10-8    (原题在文末) 知识点:      调和级数(即f(n))至今没有一个完全正确的公式,但欧拉给出过一个近似公式:(n很大时)       f(n)≈ln(n)+C+1/2*n       欧拉常数值:C≈0.57721566490153286060651209       c++ math库中,log即为ln. 题解: 公式:f(n)=ln(n)+C+1/(2*n); n很小时直接求

Given a list of non negative integers, arrange them such that they form the largest number. For example, given [3, 30, 34, 5, 9], the largest formed number is 9534330. Note: The result may be very large, so you need to return a string instead of an i

Eclipse 无法找到 该 断点,原因是编译时,字节码改变了,导致eclipse无法读取对应的行了 1.ANT编译的class Eclipse不认,因为eclipse也会编译class.怎么让它们统一呢,就是在build.xml里的javac标签里加上一句debug="true",一切就OK了. 如:<javac ... debug="true"> 链接:http://blog.csdn.net/liu251/article/details/36391

/*移除HTML5 input在type="number"时的上下小箭头*/ input::-webkit-outer-spin-button, input::-webkit-inner-spin-button{ -webkit-appearance: none; margin:; } input[type="number"]{-moz-appearance:textfield;}

真机调试免费App ID出现的问题The maximum number of apps for free development profiles has been reached.免费应用程序调试最大限度苹果免费App ID只能运行2个应用程序,当调试第三个的时候就会报这个错误,必须把之前的应用程序删除,才能调试新的 解决办法:1.连接iPhone 打开Xcode->Window->Devices     2.接着出现这个界面   3.删除其中一个,不是本次运行的应用程序 4.接着会弹框  

每一个实数都能用有理数去逼近到任意精确的程度,这就是有理数的稠密性.The rational points are dense on the number axis.

There are a number of spherical balloons spread in two-dimensional space. For each balloon, provided input is the start and end coordinates of the horizontal diameter. Since it's horizontal, y-coordinates don't matter and hence the x-coordinates of s

Given n points in the plane that are all pairwise distinct, a "boomerang" is a tuple of points (i, j, k) such that the distance between i and j equals the distance between i and k (the order of the tuple matters). Find the number of boomerangs.

Count the number of segments in a string, where a segment is defined to be a contiguous sequence of non-space characters. Please note that the string does not contain any non-printable characters. Example: Input: "Hello, my name is John" Output:

Given a non-empty array of integers, return the third maximum number in this array. If it does not exist, return the maximum number. The time complexity must be in O(n). Example 1: Input: [3, 2, 1] Output: 1 Explanation: The third maximum is 1. Examp

Given an integer, write an algorithm to convert it to hexadecimal. For negative integer, two’s complement method is used. Note: All letters in hexadecimal (a-f) must be in lowercase. The hexadecimal string must not contain extra leading 0s. If the nu

We are playing the Guess Game. The game is as follows: I pick a number from 1 to n. You have to guess which number I picked. Every time you guess wrong, I'll tell you whether the number I picked is higher or lower. However, when you guess a particula

We are playing the Guess Game. The game is as follows: I pick a number from 1 to n. You have to guess which number I picked. Every time you guess wrong, I'll tell you whether the number is higher or lower. You call a pre-defined API guess(int num) wh

Given n nodes labeled from 0 to n - 1 and a list of undirected edges (each edge is a pair of nodes), write a function to find the number of connected components in an undirected graph. Example 1: 0          3 |          | 1 --- 2    4 Given n = 5 and

Given two arrays of length m and n with digits 0-9 representing two numbers. Create the maximum number of length k <= m + n from digits of the two. The relative order of the digits from the same array must be preserved. Return an array of the k digit

Write a program to find the nth super ugly number. Super ugly numbers are positive numbers whose all prime factors are in the given prime list primes of sizek. For example, [1, 2, 4, 7, 8, 13, 14, 16, 19, 26, 28, 32] is the sequence of the first 12 s

Additive number is a positive integer whose digits can form additive sequence. A valid additive sequence should contain at least three numbers. Except for the first two numbers, each subsequent number in the sequence must be the sum of the preceding

A 2d grid map of m rows and n columns is initially filled with water. We may perform an addLand operation which turns the water at position (row, col) into a land. Given a list of positions to operate, count the number of islands after each addLand o