Tutorial Python untuk bukan pengatur cara/Nyahpepijat: Perbezaan antara semakan
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Baris 1:
=''''''Bold text''''''Bold text''''''= DEBUGGING (nyah-ralat) ==
Baris 133:
print
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Program akan menjadi lebih kompleks apabila ia mempunyai struktur kawalan. Mari kita mulakan:-
'''Apakah yang baris pertama akan dijalankan? ?'''
Baris pertama: number = 5
'''Apa yang ia buat??'''
MAsukkan number 5 di dalam pemboleh ubah (variable) number.
'''Apakah baris seterusnya?'''
baris seterusnya ialah: while number > 1:
'''Apa yang ia buat?'''
Penyataan while secara amnya menunjukkan pada ekspresi, and if it is true they do the next indented block of code, otherwise they skip the next indented block of code.
So what does it do right now?
If number > 1 is true then the next two lines will be run.
So is number > 1?
The last value put into number was 5 and 5 > 1 so yes.
So what is the next line?
Since the while was true the next line is: print ".",
What does that line do?
Prints one dot and since the statement ends with a , the next print statement will not be on a different screen line.
What is the next line?
number = number - 1 since that is following line and there are no indent changes.
What does it do?
It calculates number - 1, which is the current value of number (or 5) subtracts 1 from it, and makes that the new value of number. So basically it changes number's value from 5 to 4.
What is the next line?
Well, the indent level decreases so we have to look at what type of control structure it is. It is a while loop, so we have to go back to the while clause which is while number > 1:
What does it do?
It looks at the value of number, which is 4, and compares it to 1 and since 4 > 1 the while loop continues.
What is the next line?
Since the while loop was true, the next line is: print ".",
What does it do?
It prints a second dot on the line.
What is the next line?
No indent change so it is: number = number - 1
And what does it do?
It takes the current value of number (4), subtracts 1 from it, which gives it 3 and then finally makes 3 the new value of number.
What is the next line?
Since there is an indent change caused by the end of the while loop, the next line is: while number > 1:
What does it do?
It compares the current value of number (3) to 1. 3 > 1 so the while loop continues.
What is the next line?
Since the while loop condition was true the next line is: print ".",
And it does what?
A third dot is printed on the line.
What is the next line?
It is: number = number - 1
What does it do?
It takes the current value of number (3) subtracts from it 1 and makes the 2 the new value of number.
What is the next line?
Back up to the start of the while loop: while number > 1:
What does it do?
It compares the current value of number (2) to 1. Since 2 > 1 the while loop continues.
What is the next line?
Since the while loop is continuing: print ".",
What does it do?
It discovers the meaning of life, the universe and everything. I'm joking. (I had to make sure you were awake.) The line prints a fourth dot on the screen.
What is the next line?
It's: number = number - 1
What does it do?
Takes the current value of number (2) subtracts 1 and makes 1 the new value of number.
What is the next line?
Back up to the while loop: while number > 1:
What does the line do?
It compares the current value of number (1) to 1. Since 1 > 1 is false (one is not greater than one), the while loop exits.
What is the next line?
Since the while loop condition was false the next line is the line after the while loop exits, or: print
What does that line do?
Makes the screen go to the next line.
Why doesn't the program print 5 dots?
The loop exits 1 dot too soon.
How can we fix that?
Make the loop exit 1 dot later.
And how do we do that?
There are several ways. One way would be to change the while loop to: while number > 0: Another way would be to change the conditional to: number >= 1 There are a couple others.
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