```
for f in glob.glob('input/*/*.dat'): print f
```

outputs:

```
input/ghcnm.v3.2.2.20140611/ghcnm.tavg.v3.2.2.20140611.qca.dat
input/ghcnm.v3.2.2.20140506/ghcnm.tavg.v3.2.2.20140506.qca.dat
```

Note that these are not in the right order.  Compare with shell which always sorts its globs:

```
drj$ printf '%s\n' input/*/*.dat
input/ghcnm.v3.2.2.20140506/ghcnm.tavg.v3.2.2.20140506.qca.dat
input/ghcnm.v3.2.2.20140611/ghcnm.tavg.v3.2.2.20140611.qca.dat
```

I think the shell behaviour is better and we should be allowed to rely on glob.glob sorting its result.

Note from the documentation: "The glob module finds all the pathnames matching a specified pattern according to the rules used by the Unix shell". The Unix shell has always sorted its globs.