Converting for loops to while loops in python

3
votes

I am struggling to find an efficient way to convert these for loops to a working set of while loops. Any Suggestions? I am using 2.7

def printTTriangle(height):
 for row in range(1,height+1):
    # print row T's
    for col in range(1,row+1):
        print 'T', 
    print

Thank you all for your help!

3
pythonloopsfor-loopwhile-loopiteration
why do you wants to convert into while? for are better than while - Grijesh Chauhan
You can also use * on strings: print 'T' * 4 # TTTT - user180100
also you can use xrange instead of range, might be slightly more efficient - Claudiu

3 Answers

6
votes

It's like this:

def printTTriangle(height):
    row = 1
    while row < height+1:
        col = 1
        while col < row+1:
            print 'T', 
            col += 1
        print
        row += 1

Here's how I did it. For example, let's convert this line:

for row in range(1, height+1):

First step: create an iteration variable and initialize it in the starting value of the range:

row = 1

Second step: transform the ending value of the range into the loop condition, and careful with the indexes:

while row < height+1:

Finally, don't forget to advance the loop incrementing the iteration variable:

row += 1

Putting it all together:

row = 1
while row < height+1:
    row += 1
2
votes

You can simplify it and just use one while loop:

def printTTriangle(height):
    row = 1
    while row <= height:
        print 'T '*row
        row += 1

AND if you are not obsessed with while loops, here is a one liner:

def printTTriangle(height):
    print "\n".join(['T '*row for row in range(1, height+1)])
1
votes

You can get rid of the inner loop with string multiplication operator (*) :

def printTTriangle(height):
 j = 1
 while j <= height:
     print 'T' * j + '\n '
     j += 1