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• Started Programming Young

  6 septembre 2011, par Multimedia Mike — Programming

  I have some of the strangest memories of my struggles to jump into computer programming.

  Back To BASIC
  I remember doing some Logo programming on Apple II computers at school in 5th grade (1987 timeframe). But that was mostly driving turtle graphics. Then I remember doing some TRS-80 BASIC in 7th grade, circa 1989. Emboldened by what very little I had learned in perhaps the week or 2 we took in a science class to do this, I tried a little GW-BASIC on my family’s “IBM-PC compatible” computer (they were still called that back then). I still remember what my first program consisted of. Even back then I was interested in manipulating graphics and color on a computer screen. Thus :

  10 color 1
  20 print "This is color 1"
  30 color 2
  40 print "This is color 2"
  ...
  

  And so on through 15 colors. Hey, it did the job– it demonstrated the 15 different colors you could set in text mode.

  What’s FOR For ?
  That 7th grade computer unit in science class wasn’t very thick on computer science details. I recall working with a lab partner to transcribe code listings into a computer (and also saving my work to a storage cassette). We also developed form processing programs that would print instructions to input text followed by an “INPUT I$” statement to obtain the user’s output.

  I remember there was some situation where we needed a brief delay between input and printing. The teacher told us to use a construct of the form :

  10 FOR I = 1 TO 20000
  20 NEXT I
  

  We had to calibrate the number based on our empirical assessment of how long it lasted but I recall that the number couldn’t be much higher than about 32000, for reasons that would become clearer much later.

  Imagine my confusion when I would read and try to comprehend BASIC program code I would find in magazines. I would of course see that FOR..NEXT construct all over the place but obviously not in the context of introducing deliberate execution delays. Indeed, my understanding of one of the fundamental building blocks of computer programming — iteration — was completely skewed because of this early lesson.

  Refactoring
  Somewhere along the line, I figured out that the FOR..NEXT could be used to do the same thing a bunch of times, possibly with different values. A few years after I had written that color program, I found it again and realized that I could write it as :

  10 for I = 1 to 15
  20 color I
  30 print I
  40 next I
  

  It still took me a few more years to sort out the meaning of WHILE..WEND, though.

• Révision 21413 : bloquer l’accès aux fichiers cachés cf http://archives.rezo.net/archives/spip-de...

  30 juin 2014, par b b

• Why can I run this command from the terminal but I get an error when my python runs it from the terminal for me ?

  9 mai 2019, par mu234

  I’m trying to write a python script that basically captures webcam videos from the terminal. When I put the command in a string and use subprocess.call(script, True), I get an error, but when I literally copy/paste the same command to the terminal it works fine.

  This is my python :

  import subprocess
  
  import os
  
  if (os.path.isdir("Videos/Webcam/temp") is False):
  
      dirmake = 'mkdir Videos/Webcam/temp'
  
      subprocess.call(dirmake, True)
  
  cmd = 'ffmpeg -f v4l2 -i /dev/video0 -t 00:00:10 video.webm'
  
  subprocess.call(cmd, True)

  and this is the error

  `FileNotFoundError: [Errno 2] No such file or directory: 'ffmpeg -f v4l2 -i /dev/video0 -t 00:00:10 video.webm': 'ffmpeg -f v4l2 -i /dev/video0 -t 00:00:10 video.webm'`

  If I just run ffmpeg -f v4l2 -i /dev/video0 -t 00:00:10 video.webm from the terminal it works fine.

  Originally the video was supposed to go in Videos/Webcam/temp but I took it out to see if the error had something to do with where I was putting the video. I’m using Ubuntu 18.04.2 LTS if that makes a difference.