(Medium #6) ZigZag Conversion

Problem

The string "PAYPALISHIRING" is written in a zigzag pattern on a given number of rows like this: (you may want to display this pattern in a fixed font for better legibility)

P   A   H   N
A P L S I I G
Y   I   R

And then read line by line: "PAHNAPLSIIGYIR"

Write the code that will take a string and make this conversion given a number of rows:

string convert(string s, int numRows);

Example 1:

Input: s = "PAYPALISHIRING", numRows = 3
Output: "PAHNAPLSIIGYIR"

Example 2:

Input: s = "PAYPALISHIRING", numRows = 4
Output: "PINALSIGYAHRPI"
Explanation:

P     I    N
A   L S  I G
Y A   H R
P     I

My solution

class Solution:
    def convert(self, s: str, numRows: int) -> str:
        fig = []
        for i in range(numRows):
            fig.append('')
     
        if numRows==1:
            return s
        else:
            for i in range(len(s)):
                modnum = numRows-1
                if i%(modnum*2) < modnum:
                    fig[i%modnum] += s[i]
                else:
                    fig[modnum-i%modnum] += s[i]

            result = ''
            for i in range(len(fig)):     
                result += fig[i]
            return result

Runtime: 60ms, Memory: 14MB