How to substract a single value from column of pandas DataFrame

Question

i have one data frame suppose:

name age hb
ali  34  14
jex  16  13
aja  24  16
joy  23  12

i have a value say "5" that i want to substract from each member of column "hb"

new column could be:

hb
9
8
11
7

What is the best method to do this...

thanks and regards.

Answer 1

Simply subtract the scalar value from the pandas.Series , for numerical columns pandas would automatically broadcast the scalar value and subtract it from each element in the column. Example -

df['hb'] - 5 #Where `df` is your dataframe. 

Demo -

In [43]: df Out[43]:   name  age  hb 0  ali   34  14 1  jex   16  13 2  aja   24  16 3  joy   23  12  In [44]: df['hb'] - 5 Out[44]: 0     9 1     8 2    11 3     7 Name: hb, dtype: int64 

Answer 2

If you are using this:

df['hb'] - 5

you will get a new single column. But if you want to keep the rest then you have to use:

df['hb'] -= 5

Answer 3

You can also do this using the pandas.apply function

df.loc[:, "hb"] = df["hb"].apply(lambda x: x - 5)