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How do I insert a list at the front of another list?

insert a list `k` at the front of list `a`

a.insert(0, k)

How do I insert a list at the front of another list?

insert elements of list `k` into list `a` at position `n`

a = a[:n] + k + a[n:]

Pyhon - Best way to find the 1d center of mass in a binary numpy array

calculate the mean of the nonzero values' indices of dataframe `df`

np.flatnonzero(x).mean()

Keep only date part when using pandas.to_datetime

get date from dataframe `df` column 'dates' to column 'just_date'

df['just_date'] = df['dates'].dt.date

Removing one list from another

remove elements in list `b` from list `a`

[x for x in a if x not in b]

How do I transform a multi-level list into a list of strings in Python?

join elements of each tuple in list `a` into one string

[''.join(x) for x in a]

How do I transform a multi-level list into a list of strings in Python?

join items of each tuple in list of tuples `a` into a list of strings

list(map(''.join, a))

Matching blank lines with regular expressions

match blank lines in `s` with regular expressions

re.split('\n\\s*\n', s)

Merging items in a list - Python

merge a list of integers `[1, 2, 3, 4, 5]` into a single integer

from functools import reduce reduce(lambda x, y: 10 * x + y, [1, 2, 3, 4, 5])

Convert float to comma-separated string

Convert float 24322.34 to comma-separated string

"""{0:,.2f}""".format(24322.34)

How to pass dictionary items as function arguments in python?

pass dictionary items `data` as keyword arguments in function `my_function`

my_function(**data)

get line count

get line count of file 'myfile.txt'

sum((1 for line in open('myfile.txt')))

get line count

get line count of file `filename`

def bufcount(filename): f = open(filename) lines = 0 buf_size = (1024 * 1024) read_f = f.read buf = read_f(buf_size) while buf: lines += buf.count('\n') buf = read_f(buf_size) return lines

How to round integers in python

round 1123.456789 to be an integer

print(round(1123.456789, -1))

Sorting list based on values from another list?

sort list `X` based on values from another list `Y`

[x for y, x in sorted(zip(Y, X))]

Sorting list based on values from another list?

sorting list 'X' based on values from another list 'Y'

[x for y, x in sorted(zip(Y, X))]

How to get week number in Python?

get equivalent week number from a date `2010/6/16` using isocalendar

datetime.date(2010, 6, 16).isocalendar()[1]

Select multiple ranges of columns in Pandas DataFrame

select multiple ranges of columns 1-10, 15, 17, and 50-100 in pandas dataframe `df`

df.iloc[:, (np.r_[1:10, (15), (17), 50:100])]

Python Pandas: Multiple aggregations of the same column

apply two different aggregating functions `mean` and `sum` to the same column `dummy` in pandas data frame `df`

df.groupby('dummy').agg({'returns': [np.mean, np.sum]})

convert string to lowercase

convert string `s` to lowercase

s.lower()

convert string to lowercase

convert utf-8 string `s` to lowercase

s.decode('utf-8').lower()

How to download a file via FTP with Python ftplib

ftp.retrbinary('RETR %s' % filename, file.write)

How do I increase the timeout for imaplib requests?

handle the `urlfetch_errors ` exception for imaplib request to url `url`

urlfetch.fetch(url, deadline=10 * 60)

Output first 100 characters in a string

output first 100 characters in a string `my_string`

print(my_string[0:100])

matplotlib Legend Markers Only Once

make matplotlib plot legend put marker in legend only once

legend(numpoints=1)

Python - How to calculate equal parts of two dictionaries?

get set intersection between dictionaries `d1` and `d2`

dict((x, set(y) & set(d1.get(x, ()))) for x, y in d2.items())

load csv into 2D matrix with numpy for plotting

convert csv file 'test.csv' into two-dimensional matrix

numpy.loadtxt(open('test.csv', 'rb'), delimiter=',', skiprows=1)

Django database query: How to filter objects by date range?

filter the objects in django model 'Sample' between date range `2011-01-01` and `2011-01-31`

Sample.objects.filter(date__range=['2011-01-01', '2011-01-31'])

Django database query: How to filter objects by date range?

filter objects month wise in django model `Sample` for year `2011`

Sample.objects.filter(date__year='2011', date__month='01')

syntax for creating a dictionary into another dictionary in python

create a dictionary `{'spam': 5, 'ham': 6}` into another dictionary `d` field 'dict3'

d['dict3'] = {'spam': 5, 'ham': 6}

How to apply numpy.linalg.norm to each row of a matrix?

apply `numpy.linalg.norm` to each row of a matrix `a`

numpy.apply_along_axis(numpy.linalg.norm, 1, a)

How to merge two Python dictionaries in a single expression?

merge dictionaries form array `dicts` in a single expression

dict((k, v) for d in dicts for k, v in list(d.items()))

Python. Convert escaped utf string to utf-string

Convert escaped utf string to utf string in `your string`

print('your string'.decode('string_escape'))

Counting the number of True Booleans in a Python List

counting the number of true booleans in a python list `[True, True, False, False, False, True]`

sum([True, True, False, False, False, True])

Matplotlib.animation: how to remove white margin

set the size of figure `fig` in inches to width height of `w`, `h`

fig.set_size_inches(w, h, forward=True)

python string format() with dict with integer keys

format string with dict `{'5': 'you'}` with integer keys

'hello there %(5)s' % {'5': 'you'}

Python - converting a string of numbers into a list of int

Convert a string of numbers `example_string` separated by `,` into a list of integers

map(int, example_string.split(','))

Python - converting a string of numbers into a list of int

Convert a string of numbers 'example_string' separated by comma into a list of numbers

[int(s) for s in example_string.split(',')]

Python list of tuples to list of int

Flatten list `x`

x = [i[0] for i in x]

Python list of tuples to list of int

convert list `x` into a flat list

y = map(operator.itemgetter(0), x)

Python list of tuples to list of int

get a list `y` of the first element of every tuple in list `x`

y = [i[0] for i in x]

How do I extract all the values of a specific key from a list of dictionaries?

extract all the values of a specific key named 'values' from a list of dictionaries

results = [item['value'] for item in test_data]

ISO Time (ISO 8601) in Python

get current datetime in ISO format

datetime.datetime.now().isoformat()

ISO Time (ISO 8601) in Python

get UTC datetime in ISO format

datetime.datetime.utcnow().isoformat()

Merging data frame columns of strings into one single column in Pandas

Merge all columns in dataframe `df` into one column

df.apply(' '.join, axis=0)

pandas Subtract Dataframe with a row from another dataframe

pandas subtract a row from dataframe `df2` from dataframe `df`

pd.DataFrame(df.values - df2.values, columns=df.columns)

How can I detect DOS line breaks in a file?

read file 'myfile.txt' using universal newline mode 'U'

print(open('myfile.txt', 'U').read())

Python - read text file with weird utf-16 format

print line `line` from text file with 'utf-16-le' format

print(line.decode('utf-16-le').split())

Python - read text file with weird utf-16 format

open a text file `data.txt` in io module with encoding `utf-16-le`

file = io.open('data.txt', 'r', encoding='utf-16-le')

Finding common rows (intersection) in two Pandas dataframes

Join data of dataframe `df1` with data in dataframe `df2` based on similar values of column 'user_id' in both dataframes

s1 = pd.merge(df1, df2, how='inner', on=['user_id'])

How can I check a Python unicode string to see that it *actually* is proper Unicode?

check if string `foo` is UTF-8 encoded

foo.decode('utf8').encode('utf8')

Numpy array dimensions

get the dimensions of numpy array `a`

a.shape

Numpy array dimensions

get the dimensions of numpy array `a`

N.shape(a)

Numpy array dimensions

get the dimensions of array `a`

N.shape(a)

Numpy array dimensions

get the dimensions of numpy array `a`

a.shape

How to search a list of tuples in Python

get the indices of tuples in list of tuples `L` where the first value is 53

[i for i, v in enumerate(L) if v[0] == 53]

convert a string of bytes into an int (python)

convert string of bytes `y\xcc\xa6\xbb` into an int

struct.unpack('<L', 'y\xcc\xa6\xbb')[0]

How to get the values from a NumPy array using multiple indices

get the first row, second column; second row, first column, and first row third column values of numpy array `arr`

arr[[0, 1, 1], [1, 0, 2]]

what's a good way to combinate through a set?

create a list with permutations of string 'abcd'

list(powerset('abcd'))

Converting from a string to boolean in Python?

Convert string to boolean from defined set of strings

s in ['true', '1', 't', 'y', 'yes', 'yeah', 'yup', 'certainly', 'uh-huh']

How do I url encode in Python?

replace special characters in url 'http://spam.com/go/' using the '%xx' escape

urllib.parse.quote('http://spam.com/go/')

How can I get the output of a matplotlib plot as an SVG?

Save plot `plt` as svg file 'test.svg'

plt.savefig('test.svg')

Counting array elements in Python

count the number of elements in array `myArray`

len(myArray)

Python Embedding in C++ : ImportError: No module named pyfunction

insert directory './path/to/your/modules/' to current directory

sys.path.insert(0, './path/to/your/modules/')

How to plot with x-axis at the top of the figure?

ax.xaxis.set_ticks_position('top')

Python - Bulk Select then Insert from one DB to another

Insert records in bulk from "table1" of "master" DB to "table1" of sqlite3 `cursor` object

cursor.execute('INSERT OR REPLACE INTO master.table1 SELECT * FROM table1')

How do I use a regular expression to match a name?

Match regex '[a-zA-Z][\\w-]*\\Z' on string 'A\n'

re.match('[a-zA-Z][\\w-]*\\Z', 'A\n')

How do I use a regular expression to match a name?

match regex '[a-zA-Z][\\w-]*$' on string '!A_B'

re.match('[a-zA-Z][\\w-]*$', '!A_B')

Convert hex string to int

Convert hex string "deadbeef" to integer

int('deadbeef', 16)

Convert hex string to int

Convert hex string "a" to integer

int('a', 16)

Convert hex string to int

Convert hex string "0xa" to integer

int('0xa', 16)

Convert hex string to int

Convert hex string `s` to integer

int(s, 16)

Convert hex string to int

Convert hex string `hexString` to int

int(hexString, 16)

How to print variables without spaces between values

print variable `value ` without spaces

print('Value is "' + str(value) + '"')

How to print variables without spaces between values

Print a string `value` with string formatting

print('Value is "{}"'.format(value))

How do I convert an array to string using the jinja template engine?

Jinja join elements of array `tags` with space string ' '

{{tags | join(' ')}}

get a list of locally installed Python modules

get a list of locally installed Python modules

help('modules')

Slicing a multidimensional list

Get only first element in each of the innermost of the multidimensional list `listD`

[[[x[0]] for x in listD[i]] for i in range(len(listD))]

Sort a string in lexicographic order python

Sort a string `s` in lexicographic order

sorted(s, key=str.upper)

Sort a string in lexicographic order python

sort string `s` in lexicographic order

sorted(sorted(s), key=str.upper)

Sort a string in lexicographic order python

get a sorted list of the characters of string `s` in lexicographic order, with lowercase letters first

sorted(s, key=str.lower)

Compare Python Pandas DataFrames for matching rows

find all the rows in Dataframe 'df2' that are also present in Dataframe 'df1', for the columns 'A', 'B', 'C' and 'D'.

pd.merge(df1, df2, on=['A', 'B', 'C', 'D'], how='inner')

get keys correspond to a value in dictionary

Reverse key-value pairs in a dictionary `map`

dict((v, k) for k, v in map.items())

How to decode unicode raw literals to readable string?

decode unicode string `s` into a readable unicode literal

s.decode('unicode_escape')

What is the easiest way to convert list with str into list with int?

convert list of strings `str_list` into list of integers

[int(i) for i in str_list]

What is the easiest way to convert list with str into list with int?

convert a list with string `['1', '2', '3']` into list with integers

map(int, ['1', '2', '3'])

What is the easiest way to convert list with str into list with int?

convert list with str into list with int

list(map(int, ['1', '2', '3']))

Python BeautifulSoup Extract specific URLs

find all anchor tags in html `soup` whose url begins with `http://www.iwashere.com`

soup.find_all('a', href=re.compile('http://www\\.iwashere\\.com/'))

Python BeautifulSoup Extract specific URLs

find all anchors with a hyperlink that matches the pattern '^(?!(?:[a-zA-Z][a-zA-Z0-9+.-]*:|//))'

soup.find_all('a', href=re.compile('^(?!(?:[a-zA-Z][a-zA-Z0-9+.-]*:|//))'))

Python: How can I execute a jar file through a python script

execute a jar file 'Blender.jar' using subprocess

subprocess.call(['java', '-jar', 'Blender.jar'])

How can I insert NULL data into MySQL database with Python?

insert row into mysql database with column 'column1' set to the value `value`

cursor.execute('INSERT INTO table (`column1`) VALUES (%s)', (value,))

remove a substring from the end of a string

remove a substring ".com" from the end of string `url`

if url.endswith('.com'): url = url[:(-4)]

remove a substring from the end of a string

remove a substring ".com" from the end of string `url`

url = re.sub('\\.com$', '', url)

remove a substring from the end of a string

remove a substring ".com" from the end of string `url`

print(url.replace('.com', ''))

remove a substring from the end of a string

remove a substring `suffix` from the end of string `text`

if (not text.endswith(suffix)): return text return text[:(len(text) - len(suffix))]

Python - print tuple elements with no brackets

print each first value from a list of tuples `mytuple` with string formatting

print(', ,'.join([str(i[0]) for i in mytuple]))

Clamping floating numbers in Python?

clamping floating number `my_value` to be between `min_value` and `max_value`

max(min(my_value, max_value), min_value)

Splitting a string into words and punctuation

split a unicode string `text` into a list of words and punctuation characters with a regex

re.findall('\\w+|[^\\w\\s]', text, re.UNICODE)

How to execute raw SQL in SQLAlchemy-flask app

execute raw sql queue '<sql here>' in database `db` in sqlalchemy-flask app

result = db.engine.execute('<sql here>')

Is there a method that tells my program to quit?

quit program

sys.exit(0)