制作嵌套的for循环（Python 3.x）

Question

So what I am trying to do is make this "Triangle" in python with for loops:

But with the text like so:

0|0
1|01
2|012
3|0123
4|01234

What the output that I currently have is:

0|01234
1|01234
2|01234
3|01234
4|01234

And here is the code for the output:

def pascal(n):
    answer = ""
    for rows in range(n):
        answer = str(rows) + "|"
        for col in range(n):
            answer = answer + str(col)
        print(answer)

pascal(5)

My question is, how the heck do I make the ouput do this?(Im stumped as to what im supposed to do):

0|0
1|01
2|012
3|0123
4|01234

---

If anyone would like to see what the hell I was trying to accomplish, heres my solution

Soooooooo, this blue triangle:

turns into the pascal triangle, by "n choose k":

I was trying to figure out the for loops so I can have the basic setup done(which is the blue triangle), which you guys helped with :)

So the code that I came up with to get the n choose k is this:

def factorial(n):
    answer = 1
    for number in range(2, n+1):
       answer = answer * number
    return answer


def pascal(n):
    answer = ""
    for rows in range(n):
        answer = ""
        for col in range(rows+1):
            answer = answer + str( int(factorial(rows) / (factorial(col)*factorial(rows-(col)))) )

        print(answer)
pascal(10)

The factorial() is the exclamation point in the n choose k formula and I made the rest of the formula with this code:

factorial(rows) / (factorial(col)*factorial(rows-(col))) 

So any n that is greater than 0, makes a pascal triangle :)

Answer 1

You are close. When printing each row you don't want to go all the way to n . The inner loop should stop at rows , so change for col in range(n) to for col in range(rows+1) .

def pascal(n):
    answer = ""
    for rows in range(n):
        answer = str(rows) + "|"
        for col in range(rows+1):
            answer = answer + str(col)
        print(answer)

pascal(5)

Answer 2

Just modify the second for

Code:

def pascal(n):
    answer = ""
    for rows in range(n):
        answer = str(rows) + "|"
        for col in range(rows + 1): # Modify this
            answer = answer + str(col)
        print(answer)

pascal(5)

Why? - Because your first for is for the number of lines, the second for is for the elements in that line, you don't want to loop over, let's say, 5 again, just over the correct number of elements, in this case, it will be the number of rows.

Answer 3

Your code was correct but your inner loop shouldn't loop to n . You should replace it with rows+1 .

def pascal(n):
    answer = ""
    for rows in range(n):
        answer = str(rows) + "|"
        for col in range(rows+1):
            answer = answer + str(col)
        print(answer)

pascal(5)

output:

0|0
1|01
2|012
3|0123
4|01234

Answer 4

Honestly, I wouldn't use a for loop to do this. A while loop will be much more efficient for what you want to do. For instance:

pascal(n):
  answer=''
  answerright = ''
  i=0
  while i <= n:
    answerright += str(i)
    answer += str(i) + '|' + answerright + '\n'
    i+=1
  return answer

That will generate what you're looking for, without overly complicating the code. You don't say if you are required to use for loops, but if not, this is the better solution. In python, all for loops are really foreach loops, always remember that.

Answer 5

This should get you on the right path:

for row in range (5):
  row_string = str(row) + "|"

  for i in range(row+1):
    row_string += str(i)

  print row_string

You only want to iterate up to the current row (+1 since we're zero-indexed here) in your inner for-loop.