Real Quick Tips How to Implement Certain Python Feature

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The code in this list should only do one thing, one.

One liner conditional

value_1 if condition else value_2

Run command and capture the output plus add pipeline for another command

1stcommand = ['ls ', '-l']
2ndcommand = ['egrep', 'log']

output = subprocess.Popen(1stcommand, stdout=subprocess.PIPE, env=EBG_ENV)
output = subprocess.run(2ndcommand, stdin=pat_info.stdout, stdout=subprocess.PIPE)

#add parameter shell=True if wildcard not working
#only Popen stdout process can be pass as stdin

Opening file with generator

def openingfile(patlist):
    with open(patlist, 'r') as listfile:
        for pattern in listfile.readlines():
            yield pattern

#calling the function
for i in openingfile('list.file'):
    print(i)

Getting and update value for dictionary

dict = {}

#adding value
dict['name'] = fitri

#get value
dict.get('name')

Stripping string

text = "   hello   "

#remove left trailing char
text.lstrip()

#remove right trailing char
text.rstrip()

#remove all trailing char
text.strip()

#strip custom char, must be from either end (can be applied in both rstrip and lstrip)
text.strip('o ')

Passing file's arg to script

import argparse

#create parser object
parser = argparse.ArgumentParser()

#add argument based on positional
parser.add_argument('filename')

#parsing back the arg
print(parser.parse_args().filename)

Read and writing csv file

import csv

#reading the csv file
with open('file.csv','r') as csvfile:
    readcsv = csv.reader(csvfile)
    for row in readcsv:
        print(row)
        
#writing csv file
with open('file.csv','w') as csvfile:
    writecsv = csv.writer(csvfile)
    writecsv.writerow(['one', 'two'])

Add value to dict

sample = {
    "data":"existing"
}

#using format dictionary[key] = value
sample["latest"] = "new"

Check if key exist in dictionary

sample = {
    "data":"existing"
}
#using if else and builtin method keys()
if "data" in sample.keys():
    return True

Return default value from dictionary

database = {
    'user':'fitri',
    'id': '707'
}

#return None (or any value) if key not found in database.
database.get('fatin', None)

Passing value to generator

def generatorfunction():
    x = yield x
    print (x)
    
>>> hi = generatorfunction()
>>> hi.__next__()
>>> hi.send('Fitri')
>>> Fitri

#generator need to be started first with __next__ before proceeding sending the datatypes.

Iterating generator inside of generator

def generatorfirst(n):
    for i in range(n):
        yield i 
        
def generatorsecond(n):
    yield 'Start here'
    yield from generatorfirst()
    yiend 'End here'
    
>>> hi = generatorssecond()
>>> hi.__next__()
>>> Start here
>>> Hi.__next()
>>> 0
...x98
>>> End here

#using yield from, the generator can iterate over generator object just like loop
#the key yield from need to be inside of function

Pass output from unix command pipeline into python script

#save this infot file.py
import fileinput

with fileinput.input() as f_input:
    for line in f_input:
        print(line, end='')

>>> ls -l | python file.py

#the pipeline will pass the to the script, process and get the output.