x[cat_var].isnull().sum().sort_values(ascending=False)

my_list = ["blue", "red", "green"]

#1- Using sort or srted directly or with specifc keys
my_list.sort() #sorts alphabetically or in an ascending order for numeric data 
my_list = sorted(my_list, key=len) #sorts the list based on the length of the strings from shortest to longest. 
# You can use reverse=True to flip the order

#2- Using locale and functools 
import locale
from functools import cmp_to_key
my_list = sorted(my_list, key=cmp_to_key(locale.strcoll))

""" Calculator
----------------------------------------
"""
def addition ():
    print("Addition")
    n = float(input("Enter the number: "))
    t = 0 //Total number enter
    ans = 0
    while n != 0:
        ans = ans + n
        t+=1
        n = float(input("Enter another number (0 to calculate): "))
    return [ans,t]
def subtraction ():
    print("Subtraction");
    n = float(input("Enter the number: "))
    t = 0 //Total number enter
    sum = 0
    while n != 0:
        ans = ans - n
        t+=1
        n = float(input("Enter another number (0 to calculate): "))
    return [ans,t]
def multiplication ():
    print("Multiplication")
    n = float(input("Enter the number: "))
    t = 0 //Total number enter
    ans = 1
    while n != 0:
        ans = ans * n
        t+=1
        n = float(input("Enter another number (0 to calculate): "))
    return [ans,t]
def average():
    an = []
    an = addition()
    t = an[1]
    a = an[0]
    ans = a / t
    return [ans,t]
// main...
while True:
    list = []
    print(" My first python program!")
    print(" Simple Calculator in python by Malik Umer Farooq")
    print(" Enter 'a' for addition")
    print(" Enter 's' for substraction")
    print(" Enter 'm' for multiplication")
    print(" Enter 'v' for average")
    print(" Enter 'q' for quit")
    c = input(" ")
    if c != 'q':
        if c == 'a':
            list = addition()
            print("Ans = ", list[0], " total inputs ",list[1])
        elif c == 's':
            list = subtraction()
            print("Ans = ", list[0], " total inputs ",list[1])
        elif c == 'm':
            list = multiplication()
            print("Ans = ", list[0], " total inputs ",list[1])
        elif c == 'v':
            list = average()
            print("Ans = ", list[0], " total inputs ",list[1])
        else:
            print ("Sorry, invilid character")
    else:
        break

# Python program for implementation of Bubble Sort

def bubbleSort(arr):
	n = len(arr)

	# Traverse through all array elements
	for i in range(n-1):
	# range(n) also work but outer loop will repeat one time more than needed.

		# Last i elements are already in place
		for j in range(0, n-i-1):

			# traverse the array from 0 to n-i-1
			# Swap if the element found is greater
			# than the next element
			if arr[j] > arr[j+1] :
				arr[j], arr[j+1] = arr[j+1], arr[j]

# Driver code to test above
arr = [64, 34, 25, 12, 22, 11, 90]

bubbleSort(arr)

print ("Sorted array is:")
for i in range(len(arr)):
	print ("%d" %arr[i]),

import subprocess   #for the praat calls
import os   #for ffmpeg and the pause call at the end
#Even if we wanted all videos being rendered asynchronously, we couldn't see progress or errors
import glob #for the ambiguous files
import tempfile
audioFileDirectory = 'Audio Files'
timeList = {}
fileList = glob.glob(audioFileDirectory + '\\*.wav')
pipeList = {}
for fileName in fileList:
    arglist = ['Praat.exe', '--run', 'crosscorrelateMatch.praat', 'zeussound.wav', fileName, "0" , "300"]
    print(' '.join(arglist))
    pipe = subprocess.Popen(arglist, stdout=subprocess.PIPE)
    pipeList[fileName[len(audioFileDirectory)+1:-4]] = pipe #+1 because of back slash, -4 because .wav
#for fileName, pipe in pipeList.items():
#    text = pipe.communicate()[0].decode('utf-8')
#    timeList[fileName] = float(text[::2])
for fileName, pipe in pipeList.items():
    if float(pipe.communicate()[0].decode('utf-8')[::2]) > .0003:    #.000166 is not a match, and .00073 is a perfect match. .00053 is a tested match
        arglist = ['Praat.exe', '--run', 'crosscorrelate.praat', 'zeussound.wav', audioFileDirectory + '\\' + fileName + '.wav', "0" , "300"]
        print(' '.join(arglist))
        text = subprocess.Popen(arglist, stdout=subprocess.PIPE).communicate()[0].decode('utf-8')
        timeList[fileName] = float(text[::2])
clipLength = 10
for fileName, time in timeList.items():
    arglist = ['ffmpeg', '-i', '"'+fileName+'.mp4"', '-ss', str(time-clipLength), '-t', str(clipLength*2), '-acodec', 'copy' , '-vcodec', 'copy', '"ZEUS'+ fileName + '.mp4"']
    print(' '.join(arglist))
    os.system(' '.join(arglist))
tempFile = tempfile.NamedTemporaryFile(delete=False)
for fileName in glob.glob('ZEUS*.mp4'):
    tempFile.write(("file '" + os.path.realpath(fileName) + "'\n").encode());
tempFile.seek(0)
print(tempFile.read())
tempFile.close()
arglist = ['ffmpeg', '-safe', '0', '-f', 'concat', '-i', '"'+tempFile.name+'"', '-c', 'copy', 'ZeusMontage.mp4']
print(' '.join(arglist))
os.system(' '.join(arglist))
os.unlink(tempFile.name)    #Delete the temp file
#print(timeList)
os.system('PAUSE')

""" Currency Converter
----------------------------------------
"""
import urllib.request
import json
def currency_converter(currency_from, currency_to, currency_input):
    yql_base_url = "https://query.yahooapis.com/v1/public/yql"
    yql_query = 'select%20*%20from%20yahoo.finance.xchange%20where%20pair' \
                '%20in%20("'+currency_from+currency_to+'")'
    yql_query_url = yql_base_url + "?q=" + yql_query + "&format=json&env=store%3A%2F%2Fdatatables.org%2Falltableswithkeys"
    try:
        yql_response = urllib.request.urlopen(yql_query_url)
        try:
            json_string = str(yql_response.read())
            json_string = json_string[2:
            json_string = json_string[:-1]
            print(json_string)
            yql_json = json.loads(json_string)
            last_rate = yql_json['query']['results']['rate']['Rate']
            currency_output = currency_input * float(last_rate)
            return currency_output
        except (ValueError, KeyError, TypeError):
            print(yql_query_url)
            return "JSON format error"
    except IOError as e:
        print(str(e))
currency_input = 1
#currency codes : http://en.wikipedia.org/wiki/ISO_4217
currency_from = "USD"
currency_to = "TRY"
rate = currency_converter(currency_from, currency_to, currency_input)
print(rate)