Using for loops to create a christmas tree

Question

I am trying to create a program where you enter a number and the program creates a "christmastree" arrangement of +'s. For example if I enter the number 5 the program should print:

    +
   +++
  +++++
 +++++++
+++++++++

What I have so far is:

def holidaybush(n):
    z=n-1
    x=1
    for i in range(0,n):
        for i in range(0,z):
            print('',end='')
        for i in range(0,x):
            print('+',end='')
        for i in range(0,z):
            print('',end='')
        x=x*2
        x=x-1
        z=z-1
        print()
holidaybush(5)

It does not work quite the way I expect, even though I go through the logic and it seems to work in my head. Any help? I just learned for loops today so I may not know everything about them.

Solution 1

OK, you have two problems. First, when you go to do your indentation, you write:

print('',end='')

In python (and other languages), '' is an empty string. You should use ' '.

Second, your x incrementing logic seems to be wrong. Simply adding 2 each loop works fine, making your program:

def holidaybush(n):
    z=n-1
    x=1
    for i in range(0,n):
        for i in range(0,z):
            print(' ',end='')
        for i in range(0,x):
            print('+',end='')
        for i in range(0,z):
            print(' ',end='')
        x=x+2
        z=z-1
        print()
holidaybush(5)

Your code can be made more compact by:

• Using infix operators, replacing x=x+2 with x+=2
• range automatically starts at zero, so range(0,z) can be replaced with range(z)
• Using string multiplication, replacing your inner for loops with ' ' * z

Applying these results in:

def holidaybush(n):
    z = n - 1
    x = 1
    for i in range(n):
        print(' ' * z + '+' * x + ' ' * z)
        x+=2
        z-=1
holidaybush(5)

But you might want to stick with the verbose version.

Solution 2

how about this:

def holidaybush(n):
    for i in range(n):
        print ' ' * (n - (i + 1)),'+' * (2*i+1)

holidaybush(5)

Solution 3

You could use string.center(), just for adding another solution, this made the code more compact:

def holidaybush(n):
    for i in range(n):
        print(("+" * (i * 2 + 1)).center(n * 2 - 1))

holidaybush(5)

Solution 4

This is the very simplest code to draw Christmas tree:

for i in range(1,20,2):
    print(('*'*i).center(20))

for leg in range(3):
    print(('||').center(20))

print(('\====/').center(20))

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