Python Code Snippets

To Concat multiple values

temp_list = []

for values in li_tags:

temp_list.append(values)

concat = '#'.join(temp_list)

Default Encoding/Encoding

-*Style-1*-

import sys

reload(sys)

sys.setdefaultencoding('utf-8')

-*Style-2*-

chunk = chunk.decode('unicode-escape')

chunk = chunk.encode('ascii', 'ignore')

-*Style-3*-

# -*- coding: utf-8 -*-

Extracting from URL/URL Parsing

URL = 'https://sites.google.com/view/way2learnings/python-snippet/?brd=google'

parsed = urlparse.urlparse(URL)

if "brd" in str(url_data):

target_brand=urlparse.parse_qs(parsed.query)['brd'][0]

Batch Install or Uninstall Using PIP (Python)

create a list of libs (pip freeze > file.txt)

To Uninstall (pip uninstall -y -r file.txt)

To Install (pip install -r file.txt)

Calculating Program RunTime

import time

start = int (time.time() * 1000)

<code>

end = int (time.time() * 1000)

print (end - start) / 1000

To Clean \n \t (Meta tags)

data = re.sub('\s+',' ',data)

data = re.sub('\n|\t|^\s+\|\s+$','',data)

data = data.strip()

File Modes

r : Open text file for reading. The stream is positioned at the beginning of the file

r+ : Open for reading and writing. The stream is positioned at the beginning of the file

w : Truncate to zero length or create text file for writing. The stream is positioned at the beginning of the file

w+ : Open for reading and writing. The file is created if it does not exist, otherwise it is truncated. The stream is positioned at the beginning of the file

a : Open for writing. The file is created if it does not exist. The stream is positioned at the end of the file. Subsequent writes to the file will always end up at the current end of file

a+ : Open for reading and writing. The file is created if it does not exist. The stream is positioned at the end of the file. Subsequent writes to the file will always end up at the current end of file

Python code Debugging

We can set breakpoints in our Python script with the help of the <pdb> module. Please follow the below example.

import pdb

pdb.set_trace()

We can specify <pdb.set_trace()> anywhere in the script and set a breakpoint there. It’s extremely convenient.

Difference B/W Dict and Set

# There is only a difference of ':' in both

my_dict = {i: i * i for i in xrange(10)}

my_set = {i * i for i in xrange(10)}

print my_dict

print my_set

>>{0: 0, 1: 1, 2: 4, 3: 9, 4: 16, 5: 25, 6: 36, 7: 49, 8: 64, 9: 81}

>>set([0, 1, 4, 81, 64, 9, 16, 49, 25, 36])

Collections : Named Tuples

import collections

Point = collections.namedtuple('Point', ['x', 'y'])

p = Point(x=1.0, y=2.0)

print p.y

>>2.0

List Compare Using Lambda

>>> import collections

>>> compare = lambda x, y: collections.Counter(x) == collections.Counter(y)

>>> compare([1,2,3], [1,2,3,3])

False

>>> compare([1,2,3], [1,2,3])

True

Converting Py into EXE

To make in single exe : pyinstaller --onefile <your_script_name>.py

Regular : python your_script.py

• String Operations

sample_string ='sample@gmail.com'

Replace() : sample_string.replace('gmail','ymail')

Split() : sample_string.split('@') --> ['sample','ymail.com']

rpartition() : sample_string.rpartition('@') --> ('sample','@','ymail.com')

Sort Operations

a = [1,8,9,6,7,3,8,1,2]

print sorted(a)

#Duplicates : [1, 1, 2, 3, 6, 7, 8, 8, 9]

print sorted(set(a))

#Unique Only: [1, 2, 3, 6, 7, 8, 9]

a = [(1, 2), (4, 1), (9, 10), (13, -3)]

a.sort(key=lambda x: x[1])

print(a)

# Output: [(13, -3), (4, 1), (1, 2), (9, 10)]

Parallel Sort

data = zip(list1, list2)

data.sort()

list1, list2 = map(lambda t: list(t), zip(*data))

To get Current User Name Using pwd/getpass

try:

import pwd

except ImportError:

import getpass

pwd = None

def current_user():

if pwd:

return pwd.getpwuid(os.geteuid()).pw_name

else:

return getpass.getuser()

user_name = current_user()

File Size in Human readable format

def sizeof_fmt(num, suffix='o'):

"""Readable file size

:param num: Bytes value

:type num: int

:param suffix: Unit suffix (optionnal) default = o

:type suffix: str

:rtype: str

"""

for unit in ['', 'k', 'M', 'G', 'T', 'P', 'E', 'Z']:

if abs(num) < 1024.0:

return "%3.1f %s%s" % (num, unit, suffix)

num /= 1024.0

return "%.1f%s%s" % (num, 'Yi', suffix)

Get Image Size Using IO Operation

from io import BytesIO

img_file = BytesIO()

image.save(img_file, 'png')

image_file_size = img_file.tell()

CSV Writer and Reader

#Writer

results_tsv=open("sample.tsv","wb")

headers = ['Name','Age']

csvwriter = csv.DictWriter(results_tsv, delimiter='\t',fieldnames=headers)

csvwriter.writerow(dict((fn,fn) for fn in headers))

csvwriter.writerow({'Name':'dhamo','age':27})

#Reader

file_name = 'sample.tsv'

with open(file_name) as file_pointer:

for line in csv.DictReader(file_pointer, dialect="excel-tab"):

print line.get('Name')

Python Decorator Function

def our_decorator(func):

def function_wrapper(x,y):

print "Unfortunately i called first "

print "Subtraction : {} + {} = {}".format(x,y,x-y)

# func(x,y)

return function_wrapper

@our_decorator

def addition(x,y):

print "Addition : {} + {} = {}".format(x,y,x+y)

addition(6,2)

Factorial Calculation Using Python Decorator

factorial_nos = []

def argument_test_natural_number(fact):

def helper(x):

if type(x) == int and x > 0:

#actual function call post checking

return fact(x)

else:

raise Exception("Argument is not an integer")

return helper

#Actual function

@argument_test_natural_number

def factorial(n):

if n == 1: val = 1

else: val = n * factorial(n-1)

factorial_nos.append(val)

return val

factorial(3)

print factorial_nos

For Else Statement

data_list =['a','b','c']

for val in data_list:

if val=="aA":

print "Match Found!"

break

else:

print "No Match Found!"

Assign Value with Condition Using Next()

Next(): The next() function returns the next item from the iterator

my_list =['two','three','four']

i = next((elem for elem in my_list if elem == 'two'), None)