Nested While loop that creates directories with sub directories in Python

Question

I'm trying to write a nested while loop that will create n number of folders with n number of sub-directories. The problem with my current code is that the first folder created does not contain the sub-directories. Only the 2nd directory made contains the sub-directories. My goal is to write a program that runs a parametric sweep with groundwater modeling software, and I need these directories to save the results.

import subprocess, os

i = 1
j = 1
while i <= 2:
    path = r'C:/Users/TEvans/Desktop/Testing/slope%d' % i 
    if not os.path.exists(path): os.makedirs(path)
    os.chdir(path)
    i = i+1
    while j <= 3:
        path1 = r'C:/Users/TEvans/Desktop/Testing/slope%d/r%d' % (i, j)
        if not os.path.exists(path1): os.makedirs(path1)
        j = j+1

The os.chdir(path) is not required. The os.makedirs(path) in the outer loop is not required. The call to os.makedirs(path1) in the inner loop will create the slope%d directory if it does not exist. — Robᵩ
– Robᵩ, Commented Feb 25, 2013 at 22:01

Robᵩ · Accepted Answer · 2013-02-25 22:06:02Z

2

Some of your code is redundant, and (as others mentioned) the while is confusing your math.

Here is a simpler, nearly equivalent version:

import os
for i in (1,2):
  for j in (1,2,3):
    path1 = r'C:/Users/TEvans/Desktop/Testing/slope%d/r%d' % (i, j)
    if not os.path.exists(path1): os.makedirs(path1)

I removed the call to os.makedirs() in the outer loop since those directories will be created by the inner loop's os.makedirs().
I fixed the math for both i and j to reflect what I believe you intended.
I removed the call to os.chdir() because you are using absolute paths and the call appeared to be otherwise unnecessary.

answered Feb 25, 2013 at 22:06

Robᵩ

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Comments

wRAR · Accepted Answer · 2013-02-25 21:44:59Z

1

When os.makedirs(path1) is called for the first time i is already incremented. If you used a foor loop the code would be not only cleaner but more correct.

answered Feb 25, 2013 at 21:44

wRAR

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4 Comments

Tbevans88 Over a year ago

Thank you! I moved the increment for the first loop and it works.

wRAR Over a year ago

Consider using for with xrange. I don't see reasons for while here.

Tbevans88 Over a year ago

Ok I'll switch to a for loop. When is a while loop handy? I almost never use them.

wRAR Over a year ago

@Tbevans88 when you don't loop over an iterable or when you need something other than incrementing the iterator at the end of the loop body.

Andrew Clark · Accepted Answer · 2013-02-25 21:48:14Z

0

Your problem is that i has already been incremented before the inner while loop is entered, you could fix this by moving the i = i+1 line so that it is the last thing that is done in the while i <= 2 loop.

However a better solution would be to just use a for loop:

for i in range(1, 3):
    path = r'C:/Users/TEvans/Desktop/Testing/slope%d' % i 
    if not os.path.exists(path): os.makedirs(path)
    os.chdir(path)
    for j in range(1, 4):
        path1 = r'C:/Users/TEvans/Desktop/Testing/slope%d/r%d' % (i, j)
        if not os.path.exists(path1): os.makedirs(path1)

answered Feb 25, 2013 at 21:48

Andrew Clark

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Comments

Jesse · Accepted Answer · 2013-02-25 21:50:02Z

0

The problem is with the loop constructs. This should do the trick:

import subprocess, os

for i in range(0,2):
    path = r'C:/Users/TEvans/Desktop/Testing/slope%d' % i 
    if not os.path.exists(path): os.makedirs(path)
    os.chdir(path)
    for j in range(0,3):
        path1 = r'C:/Users/TEvans/Desktop/Testing/slope%d/r%d' % (i, j)
        if not os.path.exists(path1): os.makedirs(path1)

The 'for' construct ensures that the variable is only incremented after the entire code-block has been executed, in stead of somewhere in between, as is the case in your code fragment.

answered Feb 25, 2013 at 21:50

Jesse

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