在python中使用列表理解构建金字塔模式？

Question

Can anyone show me how to create half pyramid using list comprehension ?

For example

*
**
***

I tried but did not succeed.

I am trying to convert following code into using dictionary comprehension

for i in range(0, n): 
    for j in range(0, i+1): 
        print("* ",end="") 
    print("\r")

Answer 1

Do not use list-comprehensions for side-effect (eg like printing). List comprehensions are for building lists. You could do something hacky, like this:

>>> junk = [print("\r") or [print("* ",end='') for j in range(0, i+1)] for i in range(0, n)]

*
* *
* * *
* * * *
* * * * *
* * * * * *
* * * * * * *
* * * * * * * *
* * * * * * * * *
* * * * * * * * * * 
>>> junk
[[None], [None, None], [None, None, None], [None, None, None, None], [None, None, None, None, None], [None, None, None, None, None, None], [None, None, None, None, None, None, None], [None, None, None, None, None, None, None, None], [None, None, None, None, None, None, None, None, None], [None, None, None, None, None, None, None, None, None, None]]

But you create a needless list of junk. Don't do it.

Answer 2

You can create one line of n times the * symbol by using join on something similar to a list comprehension, namely a generator expression:

>>> ''.join('*' for _ in range(5))
'*****'

You can create output consisting of multiple lines by joining the individual lines with the newline character '\\n' (as opposed to the empty string '' like before):

>>> lines = '\n'.join(['hello', 'world'])
>>> lines
'hello\nworld'
>>> print(lines)
hello
world

I'll leave combining the two as an exercise for you.

Answer 3

Keep the print() statement out of the comprehension by returning something from the comprehension that will print as a pyramid:

n = 10

print(*['*' * i for i in range(1, n + 1)], sep='\n')

OUTPUT

> python3 test.py
*
**
***
****
*****
******
*******
********
*********
**********
> 

Answer 4

You can just write this, you no need to mention sep='\\n'

n = 5

print('\n'.join(['*'*i for i in range(1,n+1)]))

Note: You should always start your range from 1 to n+1, otherwise it will skip your first iteration.