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sort dict by value python

Get a list of pairs of key-value sorted by values in dictionary `data`

sorted(list(data.items()), key=lambda x: x[1])

sort dict by value python

sorted(list(data.items()), key=lambda x: x[1])

How do I display current time using Python + Django?

display current time

now = datetime.datetime.now().strftime('%H:%M:%S')

Find the nth occurrence of substring in a string

find the index of the second occurrence of the substring `bar` in string `foo bar bar bar`

"""foo bar bar bar""".replace('bar', 'XXX', 1).find('bar')

How do you check the presence of many keys in a Python dictinary?

check if key 'stackoverflow' and key 'google' are presented in dictionary `sites`

set(['stackoverflow', 'google']).issubset(sites)

Replace part of a string in Python?

replace string ' and ' in string `stuff` with character '/'

stuff.replace(' and ', '/')

How to use `numpy.savez` in a loop for save more than one array?

Save array at index 0, index 1 and index 8 of array `np` to tmp file `tmp`

np.savez(tmp, *[getarray[0], getarray[1], getarray[8]])

time offset

substract 1 hour and 10 minutes from current time

t = datetime.datetime.now() (t - datetime.timedelta(hours=1, minutes=10))

time offset

subtract 1 hour and 10 minutes from time object `t`

(t - datetime.timedelta(hours=1, minutes=10))

time offset

add 1 hour and 2 minutes to time object `t`

dt = datetime.datetime.combine(datetime.date.today(), t)

time offset

subtract 5 hours from the time object `dt`

dt -= datetime.timedelta(hours=5)

Manipulating binary data in Python

encode string `data` using hex 'hex' encoding

print(data.encode('hex'))

Manipulating binary data in Python

Return the decimal value for each hex character in data `data`

print(' '.join([str(ord(a)) for a in data]))

python - iterating over a subset of a list of tuples

Get all the items from a list of tuple 'l' where second item in tuple is '1'.

[x for x in l if x[1] == 1]

How to read stdin to a 2d python array of integers?

Create array `a` containing integers from stdin

a.fromlist([int(val) for val in stdin.read().split()])

Is there a way to refer to the entire matched expression in re.sub without the use of a group?

place '\' infront of each non-letter char in string `line`

print(re.sub('[_%^$]', '\\\\\\g<0>', line))

How to use regular expression in lxml xpath?

Get all `a` tags where the text starts with value `some text` using regex

doc.xpath("//a[starts-with(text(),'some text')]")

Compare elements of a list of lists and return a list

convert a list of lists `a` into list of tuples of appropriate elements form nested lists

zip(*a)

Convert list of strings to int

convert a list of strings `lst` to list of integers

[map(int, sublist) for sublist in lst]

Convert list of strings to int

convert strings in list-of-lists `lst` to ints

[[int(x) for x in sublist] for sublist in lst]

Numpy: find index of elements in one array that occur in another array

get index of elements in array `A` that occur in another array `B`

np.where(np.in1d(A, B))[0]

Split dictionary of lists into list of dictionaries

create a list where each element is a dictionary with keys 'key1' and 'key2' and values corresponding to each value in the lists referenced by keys 'key1' and 'key2' in dictionary `d`

[{'key1': a, 'key2': b} for a, b in zip(d['key1'], d['key2'])]

Split dictionary of lists into list of dictionaries

map(dict, zip(*[[(k, v) for v in value] for k, value in list(d.items())]))

Get Last Day of the Month

Get Last Day of the first month in 2002

calendar.monthrange(2002, 1)

Get Last Day of the Month

Get Last Day of the second month in 2002

calendar.monthrange(2008, 2)

Get Last Day of the Month

Get Last Day of the second month in 2100

calendar.monthrange(2100, 2)

Get Last Day of the Month

Get Last Day of the month `month` in year `year`

calendar.monthrange(year, month)[1]

Get Last Day of the Month

Get Last Day of the second month in year 2012

monthrange(2012, 2)

Get Last Day of the Month

Get Last Day of the first month in year 2000

(datetime.date(2000, 2, 1) - datetime.timedelta(days=1))

Calling an external command

Calling an external command "ls -l"

from subprocess import call

Calling an external command

Calling an external command "some_command with args"

os.system('some_command with args')

Calling an external command

Calling an external command "some_command < input_file | another_command > output_file"

os.system('some_command < input_file | another_command > output_file')

Calling an external command

Calling an external command "some_command with args"

stream = os.popen('some_command with args')

Calling an external command

Calling an external command "echo Hello World"

print(subprocess.Popen('echo Hello World', shell=True, stdout=subprocess.PIPE).stdout.read())

Calling an external command

Calling an external command "echo Hello World"

print(os.popen('echo Hello World').read())

Calling an external command

Calling an external command "echo Hello World"

return_code = subprocess.call('echo Hello World', shell=True)

Calling an external command

Calling an external command "ls"

p = subprocess.Popen('ls', shell=True, stdout=subprocess.PIPE, stderr=subprocess.STDOUT) for line in p.stdout.readlines(): print(line, end=' ') retval = p.wait()

Calling an external command

Calling an external command "ls -l"

call(['ls', '-l'])

Url decode UTF-8 in Python

decode url `url` with utf8 and print it

print(urllib.parse.unquote(url).decode('utf8'))

Url decode UTF-8 in Python

decode a urllib escaped url string `url` with `utf8`

url = urllib.parse.unquote(url).decode('utf8')

Delete letters from string

delete letters from string '12454v'

"""""".join(filter(str.isdigit, '12454v'))

applying regex to a pandas dataframe

Update row values for a column `Season` using vectorized string operation in pandas

df['Season'].str.split('-').str[0].astype(int)

Sort tuples based on second parameter

sort a list of tuples `my_list` by second parameter in the tuple

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

Find all occurrences of a substring in Python

find indexes of all occurrences of a substring `tt` in a string `ttt`

[m.start() for m in re.finditer('(?=tt)', 'ttt')]

Find all occurrences of a substring in Python

find all occurrences of a substring in a string

[m.start() for m in re.finditer('test', 'test test test test')]

re.split with spaces in python

split string `s` based on white spaces

re.findall('\\s+|\\S+', s)

Working with set_index in Pandas DataFrame

set columns `['race_date', 'track_code', 'race_number']` as indexes in dataframe `rdata`

rdata.set_index(['race_date', 'track_code', 'race_number'])

recursively go through all subdirectories and read files

recursively go through all subdirectories and files in `rootdir`

for (root, subFolders, files) in os.walk(rootdir): pass

sorting a list of dictionary values by date in python

sort a list of dictionary values by 'date' in reverse order

list.sort(key=lambda item: item['date'], reverse=True)

How to truncate a string using str.format in Python?

display first 5 characters of string 'aaabbbccc'

"""{:.5}""".format('aaabbbccc')

How do I convert a string of hexadecimal values to a list of integers?

unpack hexadecimal string `s` to a list of integer values

struct.unpack('11B', s)

Finding the index of an item given a list containing it in Python

finding the index of an item 'foo' given a list `['foo', 'bar', 'baz']` containing it

[i for i, j in enumerate(['foo', 'bar', 'baz']) if j == 'foo']

How to generate all permutations of a list in Python

generate all permutations of list `[1, 2, 3]` and list `[4, 5, 6]`

print(list(itertools.product([1, 2, 3], [4, 5, 6])))

How to generate all permutations of a list in Python

generate all permutations of a list `[1, 2, 3]`

itertools.permutations([1, 2, 3])

Remove punctuation from Unicode formatted strings

substitute occurrences of unicode regex pattern u'\\p{P}+' with empty string '' in string `text`

return re.sub('\\p{P}+', '', text)

manually throw/raise an exception

manually throw/raise a `ValueError` exception with the message 'A very specific bad thing happened'

raise ValueError('A very specific bad thing happened')

Manually raising (throwing) an exception

throw an exception "I know Python!"

raise Exception('I know Python!')

Manually raising (throwing) an exception

Manually throw an exception "I know python!"

raise Exception('I know python!')

Manually raising (throwing) an exception

throw a ValueError with message 'represents a hidden bug, do not catch this'

raise ValueError('represents a hidden bug, do not catch this')

Manually raising (throwing) an exception

throw an Exception with message 'This is the exception you expect to handle'

raise Exception('This is the exception you expect to handle')

Manually raising (throwing) an exception

throw a value error with message 'A very specific bad thing happened', 'foo', 'bar', 'baz'

raise ValueError('A very specific bad thing happened')

Manually raising (throwing) an exception

throw a runtime error with message 'specific message'

raise RuntimeError('specific message')

Manually raising (throwing) an exception

throw an assertion error with message "Unexpected value of 'distance'!", distance

raise AssertionError("Unexpected value of 'distance'!", distance)

Clear text from textarea with selenium

if Selenium textarea element `foo` is not empty, clear the field

driver.find_element_by_id('foo').clear()

Clear text from textarea with selenium

clear text from textarea 'foo' with selenium

driver.find_element_by_id('foo').clear()

Convert an IP string to a number and vice versa

convert a number 2130706433 to ip string

socket.inet_ntoa(struct.pack('!L', 2130706433))

How to rearrange Pandas column sequence?

Rearrange the columns 'a','b','x','y' of pandas DataFrame `df` in mentioned sequence 'x' ,'y','a' ,'b'

df = df[['x', 'y', 'a', 'b']]

How to call Base Class's __init__ method from the child class?

call base class's __init__ method from the child class `ChildClass`

super(ChildClass, self).__init__(*args, **kwargs)

Sum of all values in a Python dict

sum of all values in a python dict `d`

sum(d.values())

Sum of all values in a Python dict

sum(d.values())

Convert Python dictionary to JSON array

convert python dictionary `your_data` to json array

json.dumps(your_data, ensure_ascii=False)

numpy array assignment using slicing

assign an array of floats in range from 0 to 100 to a variable `values`

values = np.array([i for i in range(100)], dtype=np.float64)

Sort a list of dictionary provided an order

sort a list of dictionaries `list_of_dct` by values in an order `order`

sorted(list_of_dct, key=lambda x: order.index(list(x.values())[0]))

how to change the case of first letter of a string?

change the case of the first letter in string `s`

return s[0].upper() + s[1:]

how to change [1,2,3,4] to '1234' using python

join list of numbers `[1,2,3,4] ` to string of numbers.

"""""".join([1, 2, 3, 4])

Delete every non utf-8 symbols froms string

delete every non `utf-8` characters from a string `line`

line = line.decode('utf-8', 'ignore').encode('utf-8')

How to execute a command in the terminal from a Python script?

execute a command `command ` in the terminal from a python script

os.system(command)

Python MySQL Parameterized Queries

MySQL execute query 'SELECT * FROM foo WHERE bar = %s AND baz = %s' with parameters `param1` and `param2`

c.execute('SELECT * FROM foo WHERE bar = %s AND baz = %s', (param1, param2))

Convert a string to datetime object in python

Parse string `datestr` into a datetime object using format pattern '%Y-%m-%d'

dateobj = datetime.datetime.strptime(datestr, '%Y-%m-%d').date()