title: Python Pandas Cumulative Sum across columns and get the result in another new columns
body: <p>I have dataframe which has col1-col10, I want to calculate cumulative sum across columns and create new columns on the go i.e. cum_col1-cum_col10. I looked into cumsum(), but that gives final cumulative sum. How to achieve cumulative sum while creating new columns.</p>
  <p>Dataframe looks like:</p>
  <pre><code>id    col1 col2 col3 col4 col5 col6 col7 col8 col9 col10
  1     5    5     5   5    0    0    1    4    3    3 
  2     0    0     0   0    0    0    4    4    0    0 
  3     0    1     2   3    0    0    0    5    6    0
  </code></pre>
  <p>Expected results:</p>
  <pre><code>id  cum_col1 cum_col2 cum_col3 cum_col4 cum_col5 cum_col6 cum_col7 cum_col8 cum_col9 cum_col10
  1   5        10       15       20       20       20       21       25       28       31 
  2   0        0        0        0        0        0        4        8        8        8 
  3   0        1        3        6        6        6        6        11       17       17
  </code></pre>
  <p>The DDL to generate the dataframe:</p>
  <pre><code>import pandas as pd
  
  df = pd.DataFrame({'id': [1, 2, 3],
                     'col1': [5, 0, 0],
                     'col2': [5, 0, 1],
                     'col3': [5, 0, 2],
                     'col4': [5, 0, 3],
                     'col5' : [0, 0, 0],
                     'col6': [0, 0, 0],
                     'col7': [1, 4, 0],
                     'col8': [4, 4, 5],
                     'col9': [3, 0, 6],
                     'col10': [3, 0, 0]})
  </code></pre>
  <p>Thanks!</p>