Split array by rows

Question

I have a very basic problem.I have wrote a code which open a .txt file which contain a numbers 1 2 3 4 5 6 7 8 9.Then it square all of it and write to other file. Right now I want to add to this code procedure which split all of this numbers in rows and rewrite,like this:

1 4 9
16 25 36
49 64 81

My code already:

n=[]
dane = open("num.txt", "r")

for i in dane:
  i = i.replace('\n','')
  for j in i.split(' '):
        j = int(j)
        j = j**2
        n.append(j)

nowy = open("newnum.txt","w")
nowy.write(str(n))
nowy.close()

So what is the problem with the code?

Bhargav Rao
– Bhargav Rao

2015-03-29 10:38:34 +00:00
Commented Mar 29, 2015 at 10:38 — Bhargav Rao
– Bhargav Rao, Commented Mar 29, 2015 at 10:38
how your actual input looks like?

Avinash Raj
– Avinash Raj

2015-03-29 10:41:28 +00:00
Commented Mar 29, 2015 at 10:41 — Avinash Raj
– Avinash Raj, Commented Mar 29, 2015 at 10:41

Bhargav Rao · Accepted Answer · 2015-03-29 10:43:30Z

2

The code you have written works fine expect for the writing part. For which you need to change the last three lines of code as

nowy = open("newnum.txt","w")
for i in range(0,len(n),3):
    nowy.write("{} {} {}\n".format(n[i],n[i+1],n[i+2]))
nowy.close()

The for loop can be explained as,

loop through the list n that you have generated 3 at a time by using the third argument to the range function which is called step.
write out the values three at a time into the file, terminated by the newline character

The output after changing the lines of code is as expected

1 4 9
16 25 36
49 64 81

Ref:

answered Mar 29, 2015 at 10:43

Bhargav Rao

52.6k29 gold badges130 silver badges142 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Bhargav Rao Over a year ago

@wiedzminYo All the best :)

Sylvain Leroux · Accepted Answer · 2015-03-29 11:21:37Z

As a complement to @Bhargav's answer, according to the doc "[a] possible idiom for clustering a data series into n-length groups [is] using zip(*[iter(s)]*n)"

You can use the star to unpack a list/tuple as arguments to format function call too.

All this will lead to a more Pythonic (or, rather crypto-Pythonic ?) version of the writing part:

with open("newnum.txt","w") as nowy:
    for sublist in zip(*[iter(n)]*3):
        nowy.write("{} {} {}\n".format(*sublist))

Please note the use of a context manager (with statement) to ensure proper closing of the file in all cases when exiting from the block. As other changes would be subject to discussion, that later is a must -- and you should definitively take the habit of using it
_{(BTW, have you noticed you never closed the dane file? A simple mistake that would have been avoided by the use of a context manager to manage that resource...)}

Alexey Gorozhanov · Accepted Answer · 2015-03-29 10:46:18Z

0

You can try this:

strNew = ''
dane = open("num.txt", "r")
row = 0
for i in dane:
  i = i.replace('\n','')
  for j in i.split(' '):
    row += 1
    j = int(j)
    j = j**2
    if (row % 3) == 0:
        strNew += str(j)+'\n'
    else:
        strNew += str(j) + ' ' # it can be ' ' or '\t'

nowy = open("newnum.txt","w")
nowy.write(strNew)
nowy.close()

The result is:

1 4 9
16 25 36
49 64 81

answered Mar 29, 2015 at 10:46

Alexey Gorozhanov

70610 silver badges20 bronze badges

Comments

Ch0k0l8 · Accepted Answer · 2015-03-29 10:48:45Z

0

n=[]
dane = open("num.txt", "r")

for i in dane:
  i = i.replace('\n','')
  for j in i.split(' '):
        j = int(j)
        j = j**2
        # new code added
        # why str(j)? Because array in Python can only have one type of element such as string, int, etc. as opposed to tuple that can have multiple type in itself. I appended string because I wanna append \n at the end of each step(in outer loop I mean)
        n.append(str(j))

  # new code added
  n.append("\n")

nowy = open("newnum.txt","w")
nowy.write(str(n))
nowy.close()

answered Mar 29, 2015 at 10:48

Ch0k0l8

8476 silver badges15 bronze badges

1 Comment

PM 2Ring Over a year ago

"array in Python can only have one type of element". n is a Python list; Python doesn't have a native array type (although a Python list is implemented in CPython as an array of pointers). The elements of a Python list do not have to be of the same type. However, it's generally considered good programing style to avoid mixing types in a list (apart from special values like None), but that's a guideline, not a hard & fast rule.

Collectives™ on Stack Overflow

Split array by rows

4 Answers 4

1 Comment

Comments

Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

1 Comment

Comments

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related