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20. One-Liners¶
In this chapter I will show you some one-liner Python commands which can be really helpful.
Simple Web Server
Ever wanted to quickly share a file over a network? Well you are in luck. Python has a feature just for you. Go to the directory which you want to serve over the network and write the following code in your terminal:
# Python 2
python -m SimpleHTTPServer
# Python 3
python -m http.server
Pretty Printing
You can print a list and dictionary in a beautiful format in the Python repl. Here is the relevant code:
from pprint import pprint
my_dict = {'name': 'Yasoob', 'age': 'undefined', 'personality': 'awesome'}
print(dir(my_dict))
# ['__add__', '__class__', '__contains__', '__delattr__', '__delitem__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getitem__', '__gt__', '__hash__', '__iadd__', '__imul__', '__init__', '__init_subclass__', '__iter__', '__le__', '__len__', '__lt__', '__mul__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__reversed__', '__rmul__', '__setattr__', '__setitem__', '__sizeof__', '__str__', '__subclasshook__', 'append', 'clear', 'copy', 'count', 'extend', 'index', 'insert', 'pop', 'remove', 'reverse', 'sort']
pprint(dir(my_dict))
# ['__add__',
# '__class__',
# '__contains__',
# '__delattr__',
# '__delitem__',
# '__dir__',
# '__doc__',
# '__eq__',
# '__format__',
# '__ge__',
# '__getattribute__',
# '__getitem__',
# '__gt__',
# '__hash__',
# '__iadd__',
# '__imul__',
# '__init__',
# '__init_subclass__',
# '__iter__',
# '__le__',
# '__len__',
# '__lt__',
# '__mul__',
# '__ne__',
# '__new__',
# '__reduce__',
# '__reduce_ex__',
# '__repr__',
# '__reversed__',
# '__rmul__',
# '__setattr__',
# '__setitem__',
# '__sizeof__',
# '__str__',
# '__subclasshook__',
# 'append',
# 'clear',
# 'copy',
# 'count',
# 'extend',
# 'index',
# 'insert',
# 'pop',
# 'remove',
# 'reverse',
# 'sort']
This is more effective on nested dict s. Moreover, if you want to pretty print
json quickly from a file then you can simply do:
cat file.json | python -m json.tool
Profiling a script
This can be extremely helpful in pinpointing the bottlenecks in your scripts:
python -m cProfile my_script.py
Note: cProfile is a faster implementation of profile as it is
written in c
CSV to json
Run this in the terminal:
python -c "import csv,json;print json.dumps(list(csv.reader(open('csv_file.csv'))))"
Make sure that you replace csv_file.csv to the relevant file name.
List Flattening
You can quickly and easily flatten a list using
itertools.chain.from_iterable from the itertools package. Here
is a simple example:
a_list = [[1, 2], [3, 4], [5, 6]]
print(list(itertools.chain.from_iterable(a_list)))
# Output: [1, 2, 3, 4, 5, 6]
# or
print(list(itertools.chain(*a_list)))
# Output: [1, 2, 3, 4, 5, 6]
One-Line Constructors
Avoid a lot of boilerplate assignments when initializing a class
class A(object):
def __init__(self, a, b, c, d, e, f):
self.__dict__.update({k: v for k, v in locals().items() if k != 'self'})
Additional one-liners can be found on the Python website.