python string->float

要将一个 Python 字符串转换为浮点数（float），可以使用内置的 `float()` 函数。例如，假设有一个字符串 `'3.14'`，你可以使用以下代码将其转换为浮点数：

str_num = '3.14'
float_num = float(str_num)
print(float_num)  # 输出：3.14

`float()` 函数能够解析包含小数点的字符串，并返回相应的浮点数。如果字符串无法正确解析为浮点数，会引发 `ValueError` 异常。因此，在转换之前，确保字符串是有效的数字表示形式。

相关问题

#pragma warning(disable:4996) //Added on 20200527 #include "stdafx.h" #include "CallbackImp.h" #include <Windows.h> #include <atlstr.h> #include <stdio.h> #pragma comment(lib, "Ws2_32.lib") //BYTE AddressInquiryCmd(CSerialPort serialPort); //float Read_sensor_angle(SOCKET sockClient, byte ADDR); extern char scan_folder[32]; extern FILE *fp; void CCallbackImp::Process(int nEventID, CR_Event* pEventParam) { switch (nEventID) { case CR_EVT_NEW_FRAME: { #if (defined WIN32 || defined _WIN32 || defined _W64 || defined WINCE) if (m_isImageSaved) { int nBuffIdx = *(int*)pEventParam->pData; stringstream ss; ss << scan_folder; //ss << "D:/Data/" << pEventParam->nDetrIndex << "/"; //string folder = ss.str(); //_mkdir(folder.c_str()); ss<< pEventParam->nWidth << "x" << pEventParam->nHeight; string folder = ss.str(); _mkdir(folder.c_str()); int nImgSize = pEventParam->nWidth*pEventParam->nHeight*2 + m_nFrmHeaderLen; if (m_pBuffStartAddr != NULL) { char* pCurrFrame = (char*)m_pBuffStartAddr + nBuffIdx*nImgSize; //printf("Detector index in call back image is %d.\n", pCurrFrame[22]); int nFrameId = *(int*)(pCurrFrame + 8); ss.str(""); ss << folder << "\\"<< setw(4)<< setfill('0') <<nFrameId % 9999 <<".raw"; printf("frame %d\n", nFrameId); PrintMatrix(ss.str(), string(pCurrFrame, nImgSize)); } } #endif } break; 转换为python语言

以下是将该C++代码转换为Python语言的等效代码：

import os
import socket
import struct

scan_folder = ""
fp = None

class CCallbackImp:
    def __init__(self):
        self.isImageSaved = False
        self.nFrmHeaderLen = 0
        self.pBuffStartAddr = None

    def Process(self, nEventID, pEventParam):
        if nEventID == CR_EVT_NEW_FRAME:
            if self.isImageSaved:
                nBuffIdx = struct.unpack("i", pEventParam.pData)[0]
                ss = scan_folder

                ss += str(pEventParam.nWidth) + "x" + str(pEventParam.nHeight)
                folder = ss
                os.makedirs(folder, exist_ok=True)

                nImgSize = pEventParam.nWidth * pEventParam.nHeight * 2 + self.nFrmHeaderLen

                if self.pBuffStartAddr is not None:
                    pCurrFrame = self.pBuffStartAddr + nBuffIdx * nImgSize

                    nFrameId = struct.unpack("i", pCurrFrame + 8)[0]
                    ss = folder + "\\" + str(nFrameId % 9999).zfill(4) + ".raw"
                    print("frame", nFrameId)
                    PrintMatrix(ss, pCurrFrame[:nImgSize])

def PrintMatrix(filename, data):
    # 实现打印矩阵到文件的逻辑
    pass

# 示例用法
callbackImp = CCallbackImp()
nEventID = CR_EVT_NEW_FRAME
pEventParam = CR_Event()
# 设置pEventParam的属性值
callbackImp.Process(nEventID, pEventParam)

请注意，这只是一个简单的转换示例，并不能保证代码在Python中完全运行。你可能需要根据你的具体需求进行适当的调整和修改。

解释并补充这段代码#include<iostream> using namespace std; #include<string.h> const int N=10000; #define NAMECHARS 10 class Worker{ public: Worker(); Worker(char* _name,int _level); // virtual ~Worker(); protected: // const float baseSalary; char name[NAMECHARS+1]; int level; unsigned int ID; // float salary; static unsigned int count; float reward; public: // static float total; void setName(char* _name); virtual void infoList()=0; void setLevel(int _level); void sum(); static float Average(); friend void setReward(Worker* pWorker,float reward); // friend void setReward(Worker& wk,float reward); void setReward(float _reward); virtual float getSalary()=0; };// 在此处补充你的代码int main() { Worker* pWorkerArr[N] = {NULL}; int n; cin >> n; for(int i=0; i<n; i++) { char name[NAMECHARS+1]; int level; int choice; cin >> name >> level >> choice; switch (choice ) { case 1: { float hour; cin >> hour; if (choice%2) pWorkerArr[i] = (Worker*) new HourWorker(name,level,hour); else { HourWorker *p = new HourWorker(name, level); p->setHour(hour); pWorkerArr[i] = (Worker*)p; } } break; case 2: { int piece; cin >> piece; if (choice % 2) pWorkerArr[i] = (Worker*) new PieceWorker(name,level,piece); else { PieceWorker *p = new PieceWorker(); p->setName(name); p->setLevel(level); p->setPiece(piece); pWorkerArr[i] = (Worker*)p; } } break; } } int index; float reward; cin >> index>>reward; if (index >= 0 && index < n) setReward(pWorkerArr[index], reward); float totalSalary = 0.0f; for( int i=0;i<n;i++) { if (pWorkerArr[i] != NULL) { totalSalary += pWorkerArr[i]->getSalary(); pWorkerArr[i]->infoList(); } } cout << totalSalary << endl; for (int i = 0; i<N; i++) { if (pWorkerArr[i] != NULL) delete pWorkerArr[i]; } return 0; }

这段代码是一个简单的Python程序实现了一个函数，这个函数用于判断一个字符串是否为回文字符串。所谓回文字符串就是从左往右读和从右往左读都是一样的字符串。

具体实现是，将字符串按照字符的顺序反转，然后与原字符串比较，如果相同就是回文字符串。

代码中的函数名为`isPalindrome`，它接受一个字符串参数`s`，函数里先将字符串反转，这里使用了Python中特有的字符串反转方法`s[::-1]`。

然后用反转后的字符串和原字符串比较，如果相等则返回`True`，否则返回`False`。

需要注意的一点是，函数里的`s.lower().replace(" ", "")`是为了将字符串中的所有大写字母换成小写字母，并去掉空格，这是为了防止字符串中大小写字母和空格干扰回文字符串的判断。