Question

I have a list of files names:

names = ['aet2000','ppt2000', 'aet2001', 'ppt2001']

While I have found some functions that can work to grep character strings, I haven’t figured out how to grep all elements of a list.

for instance I would like to:

grep(names,'aet')

and get:

['aet2000','aet2001']

Sure its not too hard, but I am new to Python

---

update
The question above apparently wasn’t accurate enough. All the answers below work for the example but not for my actual data. Here is my code to make the list of file names:

years = range(2000,2011)
months = ["jan","feb","mar","apr","may","jun","jul","aug","sep","oct","nov","dec"]
variables = ["cwd","ppt","aet","pet","tmn","tmx"]     #  *variable name*  with wildcards   
tifnames = list(range(0,(len(years)*len(months)*len(variables)+1)  ))
i = 0
for variable in variables:
   for year in years:
      for month in months:
         fullname = str(variable)+str(year)+str(month)+".tif"
         tifnames[i] = fullname
         i = i+1 

Running filter(lambda x:’aet’ in x,tifnames) or the other answers return:

Traceback (most recent call last):
  File "<pyshell#89>", line 1, in <module>
    func(tifnames,'aet')
  File "<pyshell#88>", line 2, in func
    return [i for i in l if s in i]
TypeError: argument of type 'int' is not iterable

Despite the fact that tifnames is a list of character strings:

type(tifnames[1])
<type 'str'>

Do you guys see what’s going on here? Thanks again!

Answer 1

Use filter():

>>> names = ['aet2000','ppt2000', 'aet2001', 'ppt2001']
>>> filter(lambda x:'aet' in x, names)
['aet2000', 'aet2001']

with regex:

>>> import re
>>> filter(lambda x: re.search(r'aet', x), names)
['aet2000', 'aet2001']

---

In Python 3 filter returns an iterator, hence to get a list call list() on it.

>>> list(filter(lambda x:'aet' in x, names))
['aet2000', 'aet2001']

else use list-comprehension(it will work in both Python 2 and 3:

>>> [name for name in names if 'aet' in name]
['aet2000', 'aet2001']