Extra Code Samples¶
Basic list operations¶
You’re going to enjoy lists.
>>> my_list = [1, 2, 3]
>>> my_list.append(4)
>>> my_list
[1, 2, 3, 4]
>>> my_list.insert(2, 'dog')
>>> my_list
[1, 2, 'dog', 3, 4]
>>> my_list.extend([5, 6])
>>> my_list
[1, 2, 'dog', 3, 4, 5, 6]
>>> my_list.append([7, 8])
>>> my_list
[1, 2, 'dog', 3, 4, 5, 6, [7, 8]]
>>> my_list.pop(2)
'dog'
>>> my_list
[1, 2, 3, 4, 5, 6, [7, 8]]
>>> my_list.reverse()
>>> my_list
[[7, 8], 6, 5, 4, 3, 2, 1]
Lists + functional programming¶
>>> def divisible_by_2(x):
... return x % 2 == 0
...
>>>
>>> def cube(x):
... return x ** 3
...
>>>
>>> numbers = [1, 2, 3, 4, 6, 31]
>>>
>>> filter(divisible_by_2, numbers)
>>> [2, 4, 6]
>>>
>>> map(cube, numbers)
>>> [1, 8, 27, 64, 216, 29791]
Generators¶
def print_5_lines(filename):
""" Prints the first 5 lines of the given file. """
my_file = open(filename) # my_file is a generator expression
for i in range(5):
line = my_file.next()
print line
This is useful for gigantic files, such as 100MB system logs.
Filesystem tools¶
List all the .log files in a directory, including all subdirectories.
import os
import os.path
for dirpath, dirnames, filenames in os.walk("."):
for filename in [f for f in filenames if f.endswith(".log")]:
print os.path.join(dirpath, filename)
Code taken from http://stackoverflow.com/questions/954504/how-to-get-files-in-a-directory-including-all-subdirectories
Dealing with tarfiles¶
Open and read nested tarfiles, without having to write the extracted files to disk.
>>> import tarfile
>>> baz = tarfile.open('baz.tgz')
>>> bar = tarfile.open(fileobj=baz.extractfile('bar.tgz'))
>>> bar.extractfile('bar/baz.txt').read()
'This is bar/baz.txt.\n'
