execution order of expressions in a list comprehensions [duplicate]












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This question already has an answer here:




  • Understanding nested list comprehension

    2 answers




Given the following expressions: 



matrix = [[1,2,3],[4,5,6],[7,8,9]]


A matrix is created, then a list comprehension is executed to create a flat list. The comprehension runs from left to right.



flat = [x for row in matrix for x in row]


Subsequently for each row in the matrix its values are squared. How is this comprehension evaluated? 



squared = [[x**2 for x in row] for row in matrix]





python list list-comprehension







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marked as duplicate by roganjosh, juanpa.arrivillaga python
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 Nov 21 '18 at 20:01


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  • let me review that post... thanks for the reference

    – dcrearer
    Nov 21 '18 at 19:54
















0
















This question already has an answer here:




  • Understanding nested list comprehension

    2 answers




Given the following expressions: 



matrix = [[1,2,3],[4,5,6],[7,8,9]]


A matrix is created, then a list comprehension is executed to create a flat list. The comprehension runs from left to right.



flat = [x for row in matrix for x in row]


Subsequently for each row in the matrix its values are squared. How is this comprehension evaluated? 



squared = [[x**2 for x in row] for row in matrix]





python list list-comprehension







share|improve this question















marked as duplicate by roganjosh, juanpa.arrivillaga python
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 Nov 21 '18 at 20:01


This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.
















  • let me review that post... thanks for the reference

    – dcrearer
    Nov 21 '18 at 19:54














0












0








0









This question already has an answer here:




  • Understanding nested list comprehension

    2 answers




Given the following expressions: 



matrix = [[1,2,3],[4,5,6],[7,8,9]]


A matrix is created, then a list comprehension is executed to create a flat list. The comprehension runs from left to right.



flat = [x for row in matrix for x in row]


Subsequently for each row in the matrix its values are squared. How is this comprehension evaluated? 



squared = [[x**2 for x in row] for row in matrix]





python list list-comprehension







share|improve this question

















This question already has an answer here:




  • Understanding nested list comprehension

    2 answers




Given the following expressions: 



matrix = [[1,2,3],[4,5,6],[7,8,9]]


A matrix is created, then a list comprehension is executed to create a flat list. The comprehension runs from left to right.



flat = [x for row in matrix for x in row]


Subsequently for each row in the matrix its values are squared. How is this comprehension evaluated? 



squared = [[x**2 for x in row] for row in matrix]




This question already has an answer here:




  • Understanding nested list comprehension

    2 answers







python list list-comprehension




python list list-comprehension






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share|improve this question













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edited Nov 21 '18 at 19:55









timgeb

50.5k116392




50.5k116392










asked Nov 21 '18 at 19:49









dcrearerdcrearer

6542726




6542726




marked as duplicate by roganjosh, juanpa.arrivillaga python
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 Nov 21 '18 at 20:01


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marked as duplicate by roganjosh, juanpa.arrivillaga python
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 Nov 21 '18 at 20:01


This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.















  • let me review that post... thanks for the reference

    – dcrearer
    Nov 21 '18 at 19:54



















  • let me review that post... thanks for the reference

    – dcrearer
    Nov 21 '18 at 19:54

















let me review that post... thanks for the reference

– dcrearer
Nov 21 '18 at 19:54





let me review that post... thanks for the reference

– dcrearer
Nov 21 '18 at 19:54












1 Answer
1






active

oldest

votes


















0














The first comprehension is equivalent to:



flat = 

for row in matrix:

    for x in row:

        flat.append(x)


The second comprehension is equivalent to:



squared = 

for row in matrix:

    tmp = 

    for x in row:

        tmp.append(x**2)

    squared.append(tmp)


(Except for creating additional variables in the enclosing scope like x, row, tmp.)






share|improve this answer





















  • 1





    thanks for the clear concise sample...

    – dcrearer
    Nov 21 '18 at 19:57











  • @wim right, I overlooked those. The del-ing is probably unnecessary to get the point across.

    – timgeb
    Nov 21 '18 at 20:17


















1 Answer
1






active

oldest

votes








1 Answer
1






active

oldest

votes









active

oldest

votes






active

oldest

votes









0














The first comprehension is equivalent to:



flat = 

for row in matrix:

    for x in row:

        flat.append(x)


The second comprehension is equivalent to:



squared = 

for row in matrix:

    tmp = 

    for x in row:

        tmp.append(x**2)

    squared.append(tmp)


(Except for creating additional variables in the enclosing scope like x, row, tmp.)






share|improve this answer





















  • 1





    thanks for the clear concise sample...

    – dcrearer
    Nov 21 '18 at 19:57











  • @wim right, I overlooked those. The del-ing is probably unnecessary to get the point across.

    – timgeb
    Nov 21 '18 at 20:17
















0














The first comprehension is equivalent to:



flat = 

for row in matrix:

    for x in row:

        flat.append(x)


The second comprehension is equivalent to:



squared = 

for row in matrix:

    tmp = 

    for x in row:

        tmp.append(x**2)

    squared.append(tmp)


(Except for creating additional variables in the enclosing scope like x, row, tmp.)






share|improve this answer





















  • 1





    thanks for the clear concise sample...

    – dcrearer
    Nov 21 '18 at 19:57











  • @wim right, I overlooked those. The del-ing is probably unnecessary to get the point across.

    – timgeb
    Nov 21 '18 at 20:17














0












0








0







The first comprehension is equivalent to:



flat = 

for row in matrix:

    for x in row:

        flat.append(x)


The second comprehension is equivalent to:



squared = 

for row in matrix:

    tmp = 

    for x in row:

        tmp.append(x**2)

    squared.append(tmp)


(Except for creating additional variables in the enclosing scope like x, row, tmp.)






share|improve this answer















The first comprehension is equivalent to:



flat = 

for row in matrix:

    for x in row:

        flat.append(x)


The second comprehension is equivalent to:



squared = 

for row in matrix:

    tmp = 

    for x in row:

        tmp.append(x**2)

    squared.append(tmp)


(Except for creating additional variables in the enclosing scope like x, row, tmp.)







share|improve this answer














share|improve this answer



share|improve this answer








edited Nov 21 '18 at 20:17

























answered Nov 21 '18 at 19:53









timgebtimgeb

50.5k116392




50.5k116392








  • 1





    thanks for the clear concise sample...

    – dcrearer
    Nov 21 '18 at 19:57











  • @wim right, I overlooked those. The del-ing is probably unnecessary to get the point across.

    – timgeb
    Nov 21 '18 at 20:17














  • 1





    thanks for the clear concise sample...

    – dcrearer
    Nov 21 '18 at 19:57











  • @wim right, I overlooked those. The del-ing is probably unnecessary to get the point across.

    – timgeb
    Nov 21 '18 at 20:17








1




1





thanks for the clear concise sample...

– dcrearer
Nov 21 '18 at 19:57





thanks for the clear concise sample...

– dcrearer
Nov 21 '18 at 19:57













@wim right, I overlooked those. The del-ing is probably unnecessary to get the point across.

– timgeb
Nov 21 '18 at 20:17





@wim right, I overlooked those. The del-ing is probably unnecessary to get the point across.

– timgeb
Nov 21 '18 at 20:17



-

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