If there a Python function to sum all of the columns of a particular row? If not, what would be the best way to go about this? [duplicate] - python-3.x

Question

I'm going through the Khan Academy course on Statistics as a bit of a refresher from my college days, and as a way to get me up to speed on pandas & other scientific Python.
I've got a table that looks like this from Khan Academy:
| Undergraduate | Graduate | Total
-------------+---------------+----------+------
Straight A's | 240 | 60 | 300
-------------+---------------+----------+------
Not | 3,760 | 440 | 4,200
-------------+---------------+----------+------
Total | 4,000 | 500 | 4,500
I would like to recreate this table using pandas. Of course I could create a DataFrame using something like
"Graduate": {...},
"Undergraduate": {...},
"Total": {...},
But that seems like a naive approach that would both fall over quickly and just not really be extensible.
I've got the non-totals part of the table like this:
df = pd.DataFrame(
{
"Undergraduate": {"Straight A's": 240, "Not": 3_760},
"Graduate": {"Straight A's": 60, "Not": 440},
}
)
df
I've been looking and found a couple of promising things, like:
df['Total'] = df.sum(axis=1)
But I didn't find anything terribly elegant.
I did find the crosstab function that looks like it should do what I want, but it seems like in order to do that I'd have to create a dataframe consisting of 1/0 for all of these values, which seems silly because I've already got an aggregate.
I have found some approaches that seem to manually build a new totals row, but it seems like there should be a better way, something like:
totals(df, rows=True, columns=True)
or something.
Does this exist in pandas, or do I have to just cobble together my own approach?

Answer 1

Or in two steps, using the .sum() function as you suggested (which might be a bit more readable as well):
import pandas as pd
df = pd.DataFrame( {"Undergraduate": {"Straight A's": 240, "Not": 3_760},"Graduate": {"Straight A's": 60, "Not": 440},})
#Total sum per column:
df.loc['Total',:] = df.sum(axis=0)
#Total sum per row:
df.loc[:,'Total'] = df.sum(axis=1)
Output:
Graduate Undergraduate Total
Not 440 3760 4200
Straight A's 60 240 300
Total 500 4000 4500

Answer 2

append and assign
The point of this answer is to provide an in line and not an in place solution.
append
I use append to stack a Series or DataFrame vertically. It also creates a copy so that I can continue to chain.
assign
I use assign to add a column. However, the DataFrame I'm working on is in the in between nether space. So I use a lambda in the assign argument which tells Pandas to apply it to the calling DataFrame.
df.append(df.sum().rename('Total')).assign(Total=lambda d: d.sum(1))
Graduate Undergraduate Total
Not 440 3760 4200
Straight A's 60 240 300
Total 500 4000 4500
Fun alternative
Uses drop with errors='ignore' to get rid of potentially pre-existing Total rows and columns.
Also, still in line.
def tc(d):
return d.assign(Total=d.drop('Total', errors='ignore', axis=1).sum(1))
df.pipe(tc).T.pipe(tc).T
Graduate Undergraduate Total
Not 440 3760 4200
Straight A's 60 240 300
Total 500 4000 4500

Answer 3

From the original data using crosstab, if just base on your input, you just need melt before crosstab
s=df.reset_index().melt('index')
pd.crosstab(index=s['index'],columns=s.variable,values=s.value,aggfunc='sum',margins=True)
Out[33]:
variable Graduate Undergraduate All
index
Not 440 3760 4200
Straight A's 60 240 300
All 500 4000 4500
Toy data
df=pd.DataFrame({'c1':[1,2,2,3,4],'c2':[2,2,3,3,3],'c3':[1,2,3,4,5]})
# before `agg`, I think your input is the result after `groupby`
df
Out[37]:
c1 c2 c3
0 1 2 1
1 2 2 2
2 2 3 3
3 3 3 4
4 4 3 5
pd.crosstab(df.c1,df.c2,df.c3,aggfunc='sum',margins
=True)
Out[38]:
c2 2 3 All
c1
1 1.0 NaN 1
2 2.0 3.0 5
3 NaN 4.0 4
4 NaN 5.0 5
All 3.0 12.0 15

Answer 4

The original data is:
>>> df = pd.DataFrame(dict(Undergraduate=[240, 3760], Graduate=[60, 440]), index=["Straight A's", "Not"])
>>> df
Out:
Graduate Undergraduate
Straight A's 60 240
Not 440 3760
You can only use df.T to achieve recreating this table:
>>> df_new = df.T
>>> df_new
Out:
Straight A's Not
Graduate 60 440
Undergraduate 240 3760
After computing the Total by row and columns:
>>> df_new.loc['Total',:]= df_new.sum(axis=0)
>>> df_new.loc[:,'Total'] = df_new.sum(axis=1)
>>> df_new
Out:
Straight A's Not Total
Graduate 60.0 440.0 500.0
Undergraduate 240.0 3760.0 4000.0
Total 300.0 4200.0 4500.0