pandas who decides which order the columns appear code example

Example 1: python more order of columns

In [7]: cols = df.columns.tolist()
In [8]: cols
Out[8]: [0L, 1L, 2L, 3L, 4L, 'mean']

In [12]: cols = cols[-1:] + cols[:-1]

In [13]: cols
Out[13]: ['mean', 0L, 1L, 2L, 3L, 4L]
  
In [14]: df = df[cols]

Example 2: rearrange columns pandas

You could also do something like this:

df = df[['mean', '0', '1', '2', '3']]
You can get the list of columns with:

cols = list(df.columns.values)
The output will produce:

['0', '1', '2', '3', 'mean']