Reading and writing .mat files with Python

本文介绍了如何利用Python中的scipy.io模块来读取和保存Matlab的.mat文件格式。通过简单的代码示例展示了如何加载.mat文件到Python字典中,并将Python变量保存为.mat文件供Matlab使用。

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from: http://www.janeriksolem.net/2009/05/reading-and-writing-mat-files-with.html


Reading and writing .mat files with Python

If you have some old data, or find some interesting data set online, stored in Matlab's .mat file format it is possible to read this using the scipy.io module in SciPy . This is how to do it.


data = scipy.io.loadmat('test.mat')


"data" now contains a dictionary with keys corresponding to the variable names saved in the original .mat file. The variables are in array format. Saving to .mat files is equally simple. Just create a dictionary with all variables you want to save and use savemat() .


data = {}
data['x'] = x
scipy.io.savemat('test.mat',data)


This saves the array x so that it has the name "x" when read into Matlab.

x@pi:~/WiringPi/WiringPi $ sudo apt install -y python3-rpi.gpio python3-spidev python3-can # 通过 pip 安装最新版 (可选) sudo pip3 install RPi.GPIO spidev python-can Reading package lists... Done Building dependency tree... Done Reading state information... Done python3-spidev is already the newest version (20200602~200721-1+bookworm). The following additional packages will be installed: python3-msgpack python3-packaging rpi.gpio-common Suggested packages: python-can-doc The following packages will be REMOVED: python3-rpi-lgpio The following NEW packages will be installed: python3-can python3-msgpack python3-packaging python3-rpi.gpio rpi.gpio-common 0 upgraded, 5 newly installed, 1 to remove and 159 not upgraded. Need to get 301 kB of archives. After this operation, 1,467 kB of additional disk space will be used. Get:2 http://mirrors.zju.edu.cn/raspbian/raspbian bookworm/main armhf python3-packaging all 23.0-1 [32.5 kB] Get:1 http://raspbian.raspberrypi.com/raspbian bookworm/main armhf python3-msgpack armhf 1.0.3-2+b1 [62.0 kB] Get:3 http://mirrors.zju.edu.cn/raspbian/raspbian bookworm/main armhf python3-can all 4.1.0-1 [179 kB] Get:4 http://raspbian.raspberrypi.com/raspbian bookworm/main armhf rpi.gpio-common armhf 0.7.1~a4-1+b2 [6,808 B] Get:5 http://raspbian.raspberrypi.com/raspbian bookworm/main armhf python3-rpi.gpio armhf 0.7.1~a4-1+b2 [21.2 kB] Fetched 301 kB in 4s (85.8 kB/s) (Reading database ... 137316 files and directories currently installed.) Removing python3-rpi-lgpio (0.6-0~rpt1) ... Selecting previously unselected package python3-msgpack. (Reading database ... 137301 files and directories currently installed.) Preparing to unpack .../python3-msgpack_1.0.3-2+b1_armhf.deb ... Unpacking python3-msgpack (1.0.3-2+b1) ... Selecting previously unselected package python3-packaging. Preparing to unpack .../python3-packaging_23.0-1_all.deb ... Unpacking python3-packaging (23.0-1) ... Selecting previously unselected package python3-can. Preparing to unpack .../python3-can_4.1.0-1_all.deb ... Unpacking python3-can (4.1.0-1) ... Selecting previously unselected package rpi.gpio-common:armhf. Preparing to unpack .../rpi.gpio-common_0.7.1~a4-1+b2_armhf.deb ... Unpacking rpi.gpio-common:armhf (0.7.1~a4-1+b2) ... Selecting previously unselected package python3-rpi.gpio. Preparing to unpack .../python3-rpi.gpio_0.7.1~a4-1+b2_armhf.deb ... Unpacking python3-rpi.gpio (0.7.1~a4-1+b2) ... Setting up rpi.gpio-common:armhf (0.7.1~a4-1+b2) ... Setting up python3-rpi.gpio (0.7.1~a4-1+b2) ... Setting up python3-packaging (23.0-1) ... Setting up python3-msgpack (1.0.3-2+b1) ... Setting up python3-can (4.1.0-1) ... Processing triggers for man-db (2.11.2-2) ... error: externally-managed-environment × This environment is externally managed ╰─> To install Python packages system-wide, try apt install python3-xyz, where xyz is the package you are trying to install. If you wish to install a non-Debian-packaged Python package, create a virtual environment using python3 -m venv path/to/venv. Then use path/to/venv/bin/python and path/to/venv/bin/pip. Make sure you have python3-full installed. For more information visit http://rptl.io/venv note: If you believe this is a mistake, please contact your Python installation or OS distribution provider. You can override this, at the risk of breaking your Python installation or OS, by passing --break-system-packages. hint: See PEP 668 for the detailed specification. x@pi:~/WiringPi/WiringPi $
06-27
<think>我们面对的主要问题是在树莓派上安装Python包时出现的"externally-managed-environment"错误,以及安装python2包时遇到的依赖问题。根据引用[1]和之前的上下文,我们知道这个错误是由于Debian系统(树莓派OS基于Debian)引入了PEP668,禁止直接使用pip安装系统级Python包,以避免破坏系统依赖。解决方案分为两部分:1.对于Python3:使用虚拟环境或使用系统包管理器apt安装。2.对于Python2:由于树莓派OSbookworm已经不再支持Python2,我们需要寻找替代方案。具体步骤:一、解决Python3的externally-managed-environment错误方法1(推荐):使用虚拟环境步骤:a.创建虚拟环境(如果尚未安装python3-venv,先安装:`sudoaptinstallpython3-venv`)```bashpython3-mvenvmyenv#创建名为myenv的虚拟环境sourcemyenv/bin/activate#激活虚拟环境```b.在虚拟环境中使用pip安装包,这样不会影响系统环境:```bashpipinstallRPi.GPIOspidevpython-can```方法2:使用系统包安装(如果可用)```bashsudoaptinstallpython3-<package-name>```例如:```bashsudoaptinstallpython3-rpi.gpiopython3-spidevpython3-can```方法3:强制安装(不推荐,有风险)在pip命令后加上`--break-system-packages`(但可能破坏系统):```bashsudopip3installRPi.GPIO--break-system-packages```二、解决Python2的安装问题由于树莓派OSbookworm已经移除了Python2的支持,所以无法通过`apt`安装`python-pip`,`python-pil`等包。如果必须使用Python2,有两种选择:1.降级到旧版树莓派OS(如buster),但这不是推荐做法。2.使用pyenv或从源码安装Python2,然后通过pip安装所需包(同样建议在虚拟环境中操作)。但是,考虑到Python2已经停止支持,强烈建议将项目迁移到Python3。三、依赖问题解决在安装过程中,如果遇到依赖问题(如提示某些包不可用),可以尝试以下步骤:1.更新软件源并升级系统:```bashsudoaptupdatesudoaptupgrade```2.安装编译依赖(如果需要从源码构建):```bashsudoaptinstallbuild-essentialpython-devpython3-devlibffi-devlibssl-dev```四、针对用户之前的命令,修正后的操作步骤(以Python3为例):1.安装系统提供的Python3包:```bashsudoaptupdatesudoaptinstallpython3-pippython3-pilpython3-numpypython3-rpi.gpiopython3-spidevpython3-can```注意:`python3-pil`对应Pillow库,`python3-numpy`对应numpy库。2.如果系统包版本不够新,再考虑在虚拟环境中用pip安装。五、修复GPIO库安装问题如果安装RPi.GPIO时出现错误,可能是因为缺少头文件或编译工具。安装开发工具:```bashsudoaptinstallpython3-dev```六、验证安装创建测试脚本,验证GPIO库是否可用:```pythonimportRPi.GPIOasGPIOprint(GPIO.VERSION)```执行:```bashpython3test_gpio.py```根据以上方案,用户可以选择适合自己的方法解决环境管理错误和依赖问题。注意:在树莓派5上,建议使用Python3,因为Python2可能无法支持新的硬件特性。引用说明:[^1]:关于externally-managed-environment错误的官方说明,参考PEP668。</think>### 解决树莓派Python包安装问题指南 #### 一、解决`externally-managed-environment`错误 这是Debian Bookworm引入的安全机制(PEP 668),防止pip破坏系统级Python环境[^1]。解决方案如下: **方法1:使用虚拟环境(推荐)** ```bash # 创建虚拟环境 python3 -m venv ~/gpio_env # 激活环境 source ~/gpio_env/bin/activate # 在虚拟环境中安装包 pip install RPi.GPIO spidev python-can ``` **方法2:使用系统级安装** ```bash # 通过apt安装系统级包 sudo apt install python3-rpi.gpio python3-spidev python3-can ``` **方法3:强制安装(不推荐)** ```bash # 添加--break-system-packages参数 sudo pip3 install RPi.GPIO --break-system-packages ``` #### 二、解决Python2依赖问题 Debian Bookworm已移除Python2支持,替代方案: ```bash # 安装Python2兼容环境 sudo apt install python2-minimal # 创建Python2虚拟环境 python2 -m virtualenv ~/py2_env source ~/py2_env/bin/activate # 安装Python2包 pip install RPi.GPIO spidev python-can ``` #### 三、优化软件源配置 ```bash # 修复密钥警告 sudo mv /etc/apt/trusted.gpg /etc/apt/trusted.gpg.d/ sudo apt update # 添加Raspberry Pi专用源 echo "deb http://archive.raspberrypi.com/debian/ bookworm main" | sudo tee /etc/apt/sources.list.d/rpi.list ``` #### 四、验证安装 ```python # test_gpio.py import RPi.GPIO as GPIO import spidev import can print("GPIO版本:", GPIO.VERSION) print("SPI设备:", spidev.SpiDev()) print("CAN总线接口:", can.Bus()) ``` #### 五、完整解决方案流程 ```mermaid graph TD A[遇到错误] --> B{Python版本} B -->|Python3| C[创建虚拟环境] B -->|Python2| D[安装python2-minimal] C --> E[在虚拟环境中pip安装] D --> F[创建Python2虚拟环境] E --> G[验证安装] F --> G G --> H[成功运行] ``` > **关键提示**:树莓派5已全面转向Python3,建议优先使用Python3环境开发[^2]。虚拟环境能完美隔离依赖冲突,是当前最佳实践。
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