Python/Pandas subtracting numbers in a column

Question

Sorry if this is a dumb question,

I have a pandas data frame that looks kind of like this:

Col1   Col2

0      217
287    130

I'm trying to subtract the two numbers inside column 2

Answer 1

If you are trying to do subtraction between all of the elements in Col2, you can do:

sub = df['Col2'].diff()

sub will be a Series where:

Col2

NaN
-87

DataFrame.diff()

Answer 2

If i understand you question you want to do this:

res = dataFrame['Col2'][0] - dataFrame['Col2'][1]

If this is not what you are asking please fix you question or comment below.

Answer 3

You can .sum() the values in the columns and subtract that value from the first value at df.loc[0]

df
   Col1     Col2
0   0       217
1   278     130

df.loc[0] - df.loc[1:].sum()

The output:

Col1   -278
Col2     87
dtype: int64

If you only want to apply this to Col2 :

df['Col2'].loc[0] - df['Col2'].loc[1:].sum()

Output:

87

You can use this on any number of rows in your data frame:

    Col1    Col2
0   0       217
1   278     130
2   23      45
3   22      123
4   370     123 

df.loc[0] - df.loc[1:].sum()

Output:

Col1   -693
Col2   -204
dtype: int64