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Vectorizing nested for loops in list comprehension


Vectorizing nested for loops in list comprehension

By : Jeff Lin
Date : November 21 2020, 04:01 AM
I think the issue was by ths following , If you can think of a way to use map (or imap) functions rather than nested loops, you could then try using multiprocessing to fully utilise your CPU. For example, in this case:
code :
pool.map(lambda j: map(lambda i: damerau_levenshtein_distance(i, j),original_string),compare_string) 
import multiprocessing as mp
import itertools

list1 = range(5)
list2 = range(5)

def doSomething(a,b):
    return a+b #Your damerau_levenshtein_distance function goes here

def mapDoSomething(args):
    i = args[0] #An element of list2
    otherlist = args[1] #A copy of list1
    return [doSomething(i,j) for j in otherlist]

if __name__ == '__main__':
    pool = mp.Pool()
    answer = pool.imap(mapDoSomething,zip(list2,itertools.repeat(list1)))
    print(list(answer)) #imap will compute the results in the background whilst the rest of the code runs. You can therefore ask for individual lists of results, and it won't block unless the result hasn't been computed yet. To do this, you would use answer.next() or iterate over the results somewhere else. However, by converting to a list here, I'm forcing all results to finish before printing. This is only to show you it worked. For larger lists, don't do this.
    pool.close()
    pool.join()


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Nested For Loops Using List Comprehension

Nested For Loops Using List Comprehension


By : vijay pratap singh
Date : March 29 2020, 07:55 AM
help you fix your problem If I had two strings, 'abc' and 'def', I could get all combinations of them using two for loops:
code :
lst = [j + k for j in s1 for k in s2]
lst = [(j, k) for j in s1 for k in s2]
Frame two non-nested for loops in list comprehension

Frame two non-nested for loops in list comprehension


By : ccjiancui
Date : March 29 2020, 07:55 AM
wish of those help So I have the alphabet, and I want to create a dictionary where each character in the alphabet is paired with its reverse, i.e. a is paired with z, b with y, etc. , You can use the following:
code :
{x:y for (x, y) in zip(alphabet, alphabet[::-1])}
In [28]: import string

In [29]: alphabet = string.ascii_lowercase

In [30]: {x:y for (x, y) in zip(alphabet, alphabet[::-1])}
Out[30]:
{'a': 'z',
 'b': 'y',
 'c': 'x',
 'd': 'w',
 'e': 'v',
 'f': 'u',
 'g': 't',
 'h': 's',
 'i': 'r',
 'j': 'q',
 'k': 'p',
 'l': 'o',
 'm': 'n',
 'n': 'm',
 'o': 'l',
 'p': 'k',
 'q': 'j',
 'r': 'i',
 's': 'h',
 't': 'g',
 'u': 'f',
 'v': 'e',
 'w': 'd',
 'x': 'c',
 'y': 'b',
 'z': 'a'}
python list comprehension in nested loops

python list comprehension in nested loops


By : Bowen Duan
Date : November 10 2020, 03:01 PM
wish of those help You can't use a list comprehension for your second example, because you are not building a single list. List comprehensions build one list object, not two.
You could use two separate list comprehensions:
code :
d = [j for i in b if a > i for j in c]
f = [i for i in b if a <= i]
for i in b:
    if a > i:
        d.extend(c)
    else:
        f.append(i)
for i in b:
    if a > i:
        d += c
    else:
        f.append(i)
List Comprehension output different than nested for loops?

List Comprehension output different than nested for loops?


By : Bruno Verussa
Date : March 29 2020, 07:55 AM
I wish this help you Your nested loop is not equivalent to the list comprehension, because you have altered n in the inner loop:
code :
n = n**5
L = []
for n in range(3):
    for m in range(5):
        if m % 2 == 0:
            n_power_5 = n**5
            m_power_3 = m**3
            vals = (n_power_5, m_power_3)
            L.append(vals)
for n in range(3):
    for m in range(5):
        if m % 2 == 0:
            L.append((n**5, m**3))
Nested for loops in list comprehension

Nested for loops in list comprehension


By : Patrick Ndongo
Date : March 29 2020, 07:55 AM
To fix the issue you can do The for clauses go in the same order as if you had written a nested loop.
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