how to reverse the for loop in python and print the elements from left to right

Question

This is my code which i wrote in python

n = 5
row = 2 * n - 2
for i in range(n,-1,-1):
    for j in range(row):
        print(end="")

    row -=2

    for k in range(i+1):
        print('*',end=" ")

    print()

The output what is get is this

* * * * *  
* * * * 
* * * 
* * 
*

i want to print this start from left to right order for example

The expected output is :-

* * * * *
  * * * *
    * * *
      * *
        *

if it's any possible way to print the elements from left to right because in most of my program i need that logic i'm searching for it please help me and even i used reversed function for loop it will reverse the loop but i'm not getting what i expect

Filip Młynarski · Accepted Answer · 2019-12-18 14:38:30Z

4

n = 5
print(*[' '.join(' '*i + '*'*(n-i)) for i in range(n)], sep='\n')

Output:

* * * * *
  * * * *
    * * *
      * *
        *

Explanation:

for i in range(n):
    chars = ' '*i + '*'*(n-i)  #  creating list of (i) spaces followed
                                   #  by (n-i) stars to finish a line of n elements
    print(' '.join(chars))  # join prepared values with spaces

edited Dec 18, 2019 at 14:38

answered Dec 18, 2019 at 14:18

Filip Młynarski

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4 Comments

bruno desthuilliers Over a year ago

An explanation would have been fine ;-)

jeevan jeenu Over a year ago

thanks bro You use list comprehension can you give me as i wrote normal code

Filip Młynarski Over a year ago

I feel like that code is self explanatory but I'll give it a try.

chepner Over a year ago

The code is unnecessarily complicated by writing it as a single call to print.

Riccardo Bucco · Accepted Answer · 2019-12-18 14:30:45Z

0

Here is a simple solution not using list comprehension:

n = 5
for i in range(n+1):
    for j in range(i):
        print("  ", end="")
    for j in range(i+1, n+1):
        print("* ", end="")
    print()

Output:

* * * * * 
  * * * * 
    * * * 
      * * 
        *

answered Dec 18, 2019 at 14:30

Riccardo Bucco

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Comments

kukri · Accepted Answer · 2019-12-18 14:51:50Z

0

My solution - I'm new to python as well:

n = 5
c = 0
for i in range(n, 0, -1):
    print(" " * c + "*" * i)
    c += 1

or

n = 5
c = 0
while n >= 0:
    print(" " * c + "*" * n)
    n -= 1
    c += 1

answered Dec 18, 2019 at 14:51

kukri

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Comments

chepner · Accepted Answer · 2019-12-18 14:43:39Z

-1

The problem is that print itself cannot print right-justified text. But you can print a right-justified string instead of using multiple calls to print.

Here's your original code, using join instead of an inner loop:

n = 5
row = 2 * n - 2
for i in range(n,-1,-1):
    for j in range(row):
        print(end="")

    row -=2

    row_str = " ".join(["*"] * i)
    print(row_str)

And here's the modified code to make the output right-justified:

n = 5
row = 2 * n - 2
whole = row + 1
for i in range(n,-1,-1):
    for j in range(row):
        print(end="")

    row -=2

    row_str = " ".join(["*"] * i).rjust(whole)
    print(row_str)

answered Dec 18, 2019 at 14:43

chepner

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