File "C:\Users\梁静\PycharmProjects\pythonProject\1.py", line 18 ret, frame = cap.read() ^ IndentationError: expected an indented block怎么解决

这个错误通常是因为代码缩进不正确导致的。请确保 `line 18` 前面的代码块被正确地缩进。Python 使用缩进来表示代码块，一般使用 4 个空格或者一个制表符进行缩进。

下面是一个示例代码，用于读取视频文件并显示每一帧：

import cv2

cap = cv2.VideoCapture('video.mp4')

while True:
    ret, frame = cap.read()
    
    if not ret:
        break
    
    cv2.imshow('frame',frame)
    
    if cv2.waitKey(25) & 0xFF == ord('q'):
        break

cap.release()
cv2.destroyAllWindows()

请检查你的代码缩进是否正确。

相关问题

import timefrom serial import Serialimport serial.tools.list_portsimport cv2import numpy as npcap1 = cv2.VideoCapture("/Users/yankaipan/Desktop/stand.mp4")cap2 = cv2.VideoCapture("/Users/yankaipan/Desktop/apple.mp4")cap3 = cv2.VideoCapture("/Users/yankaipan/Desktop/bamboo.mp4")cap4 = cv2.VideoCapture("/Users/yankaipan/Desktop/rubbish.mp4")port_list = list(serial.tools.list_ports.comports())port_list_1 = list(port_list[2])port_serial = port_list_1[0]arduinoData = serial.Serial(port_serial, 9600)time.sleep(1)while True: while (arduinoData.inWaiting() == 0): pass dataPacket = arduinoData.readline() dataPacket = dataPacket.decode().strip() print(dataPacket) time.sleep(3) if dataPacket == "a": while cap1.isOpened(): ret, frame = cap1.read() if ret == True: cv2.imshow('Frame', frame) if cv2.waitKey(25) & 0xFF == ord('q'): break else: cap1.set(cv2.CAP_PROP_POS_FRAMES, 0) elif dataPacket == "b": while cap2.isOpened(): ret, frame = cap2.read() if ret == True: cv2.imshow('Frame', frame) if cv2.waitKey(25) & 0xFF == ord('q'): break else: cap2.set(cv2.CAP_PROP_POS_FRAMES, 0) elif dataPacket == "c": while cap3.isOpened(): ret, frame = cap3.read() if ret == True: cv2.imshow('Frame', frame) if cv2.waitKey(25) & 0xFF == ord('q'): break else: cap3.set(cv2.CAP_PROP_POS_FRAMES, 0) elif dataPacket == "d": while cap4.isOpened(): ret, frame = cap4.read() if ret == True: cv2.imshow('Frame', frame) if cv2.waitKey(25) & 0xFF == ord('q'): break else: cap4.set(cv2.CAP_PROP_POS_FRAMES, 0)cv2.destroyAllWindows()怎样修改代码能够让其中一个视频播放时，能够触发另一视频并播放？

你可以在每个视频播放的while循环中添加一个判断语句，当某个视频播放到一定程度时触发另一个视频的播放。例如：

if ret == True:
    cv2.imshow('Frame', frame)
    if cv2.waitKey(25) & 0xFF == ord('q'):
        break
    # 视频1播放到一定程度时触发播放视频2
    if cap1.get(cv2.CAP_PROP_POS_FRAMES) == 50:
        arduinoData.write(b'b')
else:
    cap1.set(cv2.CAP_PROP_POS_FRAMES, 0)

其中，`cap1.get(cv2.CAP_PROP_POS_FRAMES)`可以获取当前视频1的播放帧数，当播放到第50帧时触发播放视频2的信号发送。你可以根据需要修改这个触发条件，以及发送的信号和对应的视频播放。

import time from serial import Serial import serial.tools.list_ports import cv2 import numpy as np cap1=cv2.VideoCapture("/Users/yankaipan/Desktop/stand.mp4") cap2=cv2.VideoCapture("/Users/yankaipan/Desktop/apple.mp4") cap3=cv2.VideoCapture("/Users/yankaipan/Desktop/bamboo.mp4") cap4=cv2.VideoCapture("/Users/yankaipan/Desktop/rubbish.mp4") port_list = list(serial.tools.list_ports.comports()) port_list_1 =list(port_list[2]) port_serial = port_list_1[0] arduinoData=serial.Serial(port_serial,9600) time.sleep(1) current_video=None #记录当前正在播放的视频 while True: while (arduinoData.inWaiting()==0): pass dataPacket=arduinoData.readline() dataPacket=dataPacket.decode().strip() print(dataPacket) time.sleep(3) # if dataPacket=="b": # print("1") # else: # print('2') if dataPacket=="a": if current_video!=cap1: #判断是否需要切换视频 if current_video is not None: current_video.release() current_video=cap1 while(cap1.isOpened()): ret, frame = cap1.read() if ret == True: cv2.imshow('Frame', frame) if cv2.waitKey(25) & 0xFF == ord('q'): break else: cap1.set(cv2.CAP_PROP_POS_FRAMES,0) current_video.set(cv2.CAP_PROP_FRAMES,0) elif dataPacket=="b": if current_video!=cap2: #判断是否需要切换视频 if current_video is not None: current_video.release() current_video=cap2 while(cap2.isOpened()): ret, frame = cap2.read() if ret == True: cv2.imshow('Frame', frame) if cv2.waitKey(25) & 0xFF == ord('q'): break else: #cap2.set(cv2.CAP_PROP_POS_FRAMES,0) current_video.set(cv2.CAP_PROP_FRAMES,0) elif dataPacket=="c": if current_video!=cap3: #判断是否需要切换视频 if current_video is not None: current_video.release() current_video=cap3 while(cap3.isOpened()): ret, frame = cap3.read() if ret == True: cv2.imshow('Frame', frame) if cv2.waitKey(25) & 0xFF == ord('q'): break else: #cap3.set(cv2.CAP_PROP_POS_FRAMES,0) current_video.set(cv2.CAP_PROP_FRAMES,0) elif dataPacket=="d": if current_video!=cap4: #判断是否需要切换视频 if current_video is not None: current_video.release() current_video=cap4 while(cap4.isOpened()): ret, frame = cap4.read() if ret == True: cv2.imshow('Frame', frame) if cv2.waitKey(25) & 0xFF == ord('q'): break else: #cap4.set(cv2.CAP_PROP_POS_FRAMES,0) current_video.set(cv2.CAP_PROP_FRAMES,0) cv2.destroyAllWindows()代码运行播放a视频时接收到其他b或c或d；并不能播放相应的视频，该怎样修改代码才能让代码运行时实现这一功能？

在你的代码中，当收到指令时，会先判断当前播放的视频是不是需要切换的视频，如果是则释放当前视频，播放新的视频。但是在播放新的视频时，你使用了一个 while 循环读取视频帧并显示，这个循环是不会退出的，直到视频播放完毕或者用户按下 'q' 键退出。因此，即使收到了其他指令，也无法立即停止当前的视频播放。

为了解决这个问题，你可以在收到新指令时，先将当前正在播放的视频暂停或者停止，然后释放视频资源，最后根据接收到的指令切换到相应的视频，并开始播放新的视频。下面是修改后的代码：

import time
from serial import Serial
import serial.tools.list_ports
import cv2
import numpy as np

cap1 = cv2.VideoCapture("/Users/yankaipan/Desktop/stand.mp4")
cap2 = cv2.VideoCapture("/Users/yankaipan/Desktop/apple.mp4")
cap3 = cv2.VideoCapture("/Users/yankaipan/Desktop/bamboo.mp4")
cap4 = cv2.VideoCapture("/Users/yankaipan/Desktop/rubbish.mp4")

port_list = list(serial.tools.list_ports.comports())
port_list_1 = list(port_list[2])
port_serial = port_list_1[0]
arduinoData = serial.Serial(port_serial, 9600)
time.sleep(1)

current_video = None  # 记录当前正在播放的视频
while True:
    while (arduinoData.inWaiting() == 0):
        pass
    dataPacket = arduinoData.readline()
    dataPacket = dataPacket.decode().strip()
    print(dataPacket)
    time.sleep(3)

    # 停止当前视频的播放
    if current_video is not None:
        current_video.release()

    # 切换到新的视频
    if dataPacket == "a":
        current_video = cap1
    elif dataPacket == "b":
        current_video = cap2
    elif dataPacket == "c":
        current_video = cap3
    elif dataPacket == "d":
        current_video = cap4

    # 开始播放新的视频
    if current_video is not None:
        current_video.set(cv2.CAP_PROP_POS_FRAMES, 0) # 将视频设置为第一帧
        while (current_video.isOpened()):
            ret, frame = current_video.read()
            if ret == True:
                cv2.imshow('Frame', frame)
                if cv2.waitKey(25) & 0xFF == ord('q'):
                    break
            else:
                current_video.set(cv2.CAP_PROP_POS_FRAMES, 0)

cv2.destroyAllWindows()

在修改后的代码中，当收到新指令时，会先停止当前视频的播放，并释放资源。然后根据指令选择新的视频并开始播放。在播放新的视频时，每次读取一帧并显示，如果用户按下 'q' 键，则退出循环停止视频播放。