Printing X-type pattern in Python 2.7

Question

I'm trying to print this pattern in Python:

    *............*
    .**........**
    ..***....***
    ...********
    ...********
    ..***....***
    .**........**
    *............*

And came up with this code that does the job:

for row in range(1,5):
    print "." * (row -1) + row * "*" + (16 - row * 4) * "." + row * "*"
for row in range (0,4):
    print("." * (3-row)+ "*" *(4 -row) + row * 4 * "." +"*" *(4 -row))

My question: is it possible to do this without using two loops? BTW, this is not for homework, I'm just playing around with some exercises from "Think Like a Programmer" by V. Anton Spraul and implementing the solutions in Python rather than C++.

Thanks in advance.

Answer 1

Without changing anything else, you can just do the loop over two ranges:

for row in range(1,5)+range(4,0,-1):
    print "." * (row -1) + row * "*" + (16 - row * 4) * "." + row * "*"

Since you can add lists together:

In [8]: range(1,5)
Out[8]: [1, 2, 3, 4]

In [9]: range(4,0,-1)
Out[9]: [4, 3, 2, 1]

In [10]: range(1,5) + range(4,0,-1)
Out[10]: [1, 2, 3, 4, 4, 3, 2, 1]

By the way, you can get rid of the leading dots using spaces:

for row in range(1,5)+range(4,0,-1):
    print " " * (row -1) + row * "*" + (16 - row * 4) * "." + row * "*"

*............*
 **........**
  ***....***
   ********
   ********
  ***....***
 **........**
*............*

---

A more elegant thing to do might be to build a list of strings:

X = []
for row in range(1,5):
    X.append(" " * (row -1) + row * "*" + (16 - row * 4) * "." + row * "*")

Now, add the bottom half by just duplicating the top half in reverse:

X = X + list(reversed(X))

But when we print it we see a list:

print X
#['*............*', ' **........**', '  ***....***', '   ********', '   ********', '  ***....***', ' **........**', '*............*']

So we can join them together with newlines:

print '\n'.join(X)

*............*
 **........**
  ***....***
   ********
   ********
  ***....***
 **........**
*............*