Max and Min value for each colum of one Dataframe

Give this dataframe ‘x’:

    col1 col2 col3 col4
    0     5   -2    1 
   -5     2   -1    9
    3    -7    3    5

How I could get a list of pairs with the min and max of each column? The result would be:

list = [ [-5 , 3], [-7 , 5], [-2 , 3], [1 , 9] ]

Answer

You could define a function and call apply passing the function name, this will create a df with min and max as the index names:

In [203]:

def minMax(x):
    return pd.Series(index=['min','max'],data=[x.min(),x.max()])


df.apply(minMax)
Out[203]:
     col1  col2  col3  col4
min    -5    -7    -2     1
max     3     5     3     9

If you insist on a list of lists we can transpose the df and convert the values to a list:

In [206]:

def minMax(x):
    return pd.Series(index=['min','max'],data=[x.min(),x.max()])


df.apply(minMax).T.values.tolist()
Out[206]:
[[-5, 3], [-7, 5], [-2, 3], [1, 9]]

The function itself is not entirely necessary as you can use a lambda instead:

In [209]:

df.apply(lambda x: pd.Series([x.min(), x.max()])).T.values.tolist()
Out[209]:
[[-5, 3], [-7, 5], [-2, 3], [1, 9]]

Note also that you can use describe and loc to get what you want:

In [212]:

df.describe().loc[['min','max']]
Out[212]:
     col1  col2  col3  col4
min    -5    -7    -2     1
max     3     5     3     9