You could also do something like df = df[['x', 'y', 'a', 'b']]
import pandas as pd
frame = pd.DataFrame({'one thing':[1,2,3,4],'second thing':[0.1,0.2,1,2],'other thing':['a','e','i','o']})
frame = frame[['second thing', 'other thing', 'one thing']]
print frame
second thing other thing one thing
0 0.1 a 1
1 0.2 e 2
2 1.0 i 3
3 2.0 o 4
Also, you can get the list of columns with:
cols = list(df.columns.values)
The output will produce something like this:
['x', 'y', 'a', 'b']
Which is then easy to rearrange manually.