Python:循环内仅打印一次 [英] Python: Print only one time inside a loop

问题描述

我有一个要从相机捕获视频的代码.我想使用Python的Logging库在外壳上获取消息或将其导出到文本文件.

I have a code where I want capture a video from a camera. I want to use Logging library of Python to get messages on the shell or export them to a text file.

这是我的代码的一部分，在while循环中，我要打印成功打开的相机

Here is a part of my code where inside the while loop I want to print Camera Opened Successfully

import numpy as np
import cv2
import logging as log

cap = cv2.VideoCapture('5.mpg')

while True:

    ret, image = cap.read()

    if ret == True:
        log.warning('Camera Opened Successfully')

    gray = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)
    clahe = cv2.createCLAHE(clipLimit = 15.0, tileGridSize=(8,8))
    gray1 = clahe.apply(gray)

但是我在shell中得到的是这样:

but what I get in the shell is this:

直到我终止正在运行的脚本.关于如何使其仅打印一次的任何想法.

until I terminated the running script. Any idea on how to make it print only once.

推荐答案

import numpy as np
import cv2
import logging as log

cap = cv2.VideoCapture('5.mpg')
hasOpened = False

while True:

    ret, image = cap.read()

    if ret and not hasOpened:
        log.warning('Camera Opened Successfully')
        hasOpened = True

如果要在打印后退出循环，请遵循Matt的回答.此选项将在循环中继续，并且仅打印一次.

If you want to break out of the loop after printing, follow Matt's answer. This option will continue in the loop and only print once.

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