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1

I would like to apply an arbitrary function to two or more nested lists of the same shape. For instance if my function is:

def add(a, b):
 if "NULL" not in [a, b]:
 return a + b
 else:
 return "NULL"

and my inputs are:

input1 = [[1, 2, "NULL"], [3, 4], [5, 6, 7, 8]]
input2 = [[9, 8, "NULL"], [7, 6], [5, 4, 3, 2]]

Then I would like the output to be

output = [[10, 10, "NULL"], [10, 10], [10, 10, 10, 10]]

The inputs will always be nested one level deep, but the outputs ideally should be anything (for instance it could be nested deeper if the function was a "concatenate(a, b)" function)

python list

share|improve this question

edited Mar 28 at 21:30

AAC

asked Mar 28 at 20:54

AACAAC

21611 silver badge99 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Will the lists only ever be nested one level deep?
  
  – Peter Collingridge
  Mar 28 at 21:08
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @PeterCollingridge Yes, at least in the input stage (perhaps the output could be nested deeper depending on the function applied)
  
  – AAC
  Mar 28 at 21:24
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  If the lists are nested one level deep aways, why not [func(val) for val in list_of_lists] or event map(func, list_of_lists), it would simplify your function.
  
  – geckos
  Mar 28 at 21:30
  

  
  
  
  

add a comment
 | 

1

I would like to apply an arbitrary function to two or more nested lists of the same shape. For instance if my function is:

def add(a, b):
 if "NULL" not in [a, b]:
 return a + b
 else:
 return "NULL"

and my inputs are:

input1 = [[1, 2, "NULL"], [3, 4], [5, 6, 7, 8]]
input2 = [[9, 8, "NULL"], [7, 6], [5, 4, 3, 2]]

Then I would like the output to be

output = [[10, 10, "NULL"], [10, 10], [10, 10, 10, 10]]

The inputs will always be nested one level deep, but the outputs ideally should be anything (for instance it could be nested deeper if the function was a "concatenate(a, b)" function)

python list

share|improve this question

edited Mar 28 at 21:30

AAC

asked Mar 28 at 20:54

AACAAC

21611 silver badge99 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Will the lists only ever be nested one level deep?
  
  – Peter Collingridge
  Mar 28 at 21:08
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @PeterCollingridge Yes, at least in the input stage (perhaps the output could be nested deeper depending on the function applied)
  
  – AAC
  Mar 28 at 21:24
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  If the lists are nested one level deep aways, why not [func(val) for val in list_of_lists] or event map(func, list_of_lists), it would simplify your function.
  
  – geckos
  Mar 28 at 21:30
  

  
  
  
  

add a comment
 | 

I would like to apply an arbitrary function to two or more nested lists of the same shape. For instance if my function is:

def add(a, b):
 if "NULL" not in [a, b]:
 return a + b
 else:
 return "NULL"

and my inputs are:

input1 = [[1, 2, "NULL"], [3, 4], [5, 6, 7, 8]]
input2 = [[9, 8, "NULL"], [7, 6], [5, 4, 3, 2]]

Then I would like the output to be

output = [[10, 10, "NULL"], [10, 10], [10, 10, 10, 10]]

The inputs will always be nested one level deep, but the outputs ideally should be anything (for instance it could be nested deeper if the function was a "concatenate(a, b)" function)

python list

share|improve this question

edited Mar 28 at 21:30

AAC

asked Mar 28 at 20:54

AACAAC

21611 silver badge99 bronze badges

def add(a, b):
 if "NULL" not in [a, b]:
 return a + b
 else:
 return "NULL"

input1 = [[1, 2, "NULL"], [3, 4], [5, 6, 7, 8]]
input2 = [[9, 8, "NULL"], [7, 6], [5, 4, 3, 2]]

output = [[10, 10, "NULL"], [10, 10], [10, 10, 10, 10]]

share|improve this question

edited Mar 28 at 21:30

AAC

asked Mar 28 at 20:54

AACAAC

21611 silver badge99 bronze badges

share|improve this question

edited Mar 28 at 21:30

AAC

asked Mar 28 at 20:54

AACAAC

21611 silver badge99 bronze badges

asked Mar 28 at 20:54

AACAAC

21611 silver badge99 bronze badges

asked Mar 28 at 20:54

AACAAC

21611 silver badge99 bronze badges

2 Answers
2

active

oldest

votes

2

How about:

def apply_f(a, b, f):
 if isinstance(a, list):
 return [apply_f(item_a, item_b, f) for item_a, item_b in zip(a, b)]
 else:
 return f(a, b)

result = apply_f(input1, input2, add)

share|improve this answer

answered Mar 28 at 21:30

Peter CollingridgePeter Collingridge

8,52733 gold badges3434 silver badges5454 bronze badges

add a comment
 | 

0

Assuming the lists are always the right length (you can put a check for this), make your function recursive:

def add(a, b):

 if isinstance(a, list) and isinstance(b, list):
 for a_sub, b_sub in zip(a, b):
 return [add(a_sub, b_sub) for a_sub, b_sub in zip(a, b)]

 elif "NULL" not in [a, b]:
 return a + b

 elif "NULL" in [a, b]:
 return "NULL"

 else:
 raise ValueError("Wrong input shapes")

input1 = [[1, 2, "NULL"], [3, 4], [5, 6, 7, 8]]
input2 = [[9, 8, "NULL"], [7, 6], [5, 4, 3, 2]]

add(input1, input2)

Output:

[[10, 10, 'NULL'], [10, 10], [10, 10, 10, 10]]

share|improve this answer

answered Mar 28 at 21:29

dzangdzang

60933 silver badges1010 bronze badges

add a comment
 | 

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2

How about:

def apply_f(a, b, f):
 if isinstance(a, list):
 return [apply_f(item_a, item_b, f) for item_a, item_b in zip(a, b)]
 else:
 return f(a, b)

result = apply_f(input1, input2, add)

share|improve this answer

answered Mar 28 at 21:30

Peter CollingridgePeter Collingridge

8,52733 gold badges3434 silver badges5454 bronze badges

add a comment
 | 

2

How about:

def apply_f(a, b, f):
 if isinstance(a, list):
 return [apply_f(item_a, item_b, f) for item_a, item_b in zip(a, b)]
 else:
 return f(a, b)

result = apply_f(input1, input2, add)

share|improve this answer

answered Mar 28 at 21:30

Peter CollingridgePeter Collingridge

8,52733 gold badges3434 silver badges5454 bronze badges

add a comment
 | 

How about:

def apply_f(a, b, f):
 if isinstance(a, list):
 return [apply_f(item_a, item_b, f) for item_a, item_b in zip(a, b)]
 else:
 return f(a, b)

result = apply_f(input1, input2, add)

share|improve this answer

answered Mar 28 at 21:30

Peter CollingridgePeter Collingridge

8,52733 gold badges3434 silver badges5454 bronze badges

def apply_f(a, b, f):
 if isinstance(a, list):
 return [apply_f(item_a, item_b, f) for item_a, item_b in zip(a, b)]
 else:
 return f(a, b)

result = apply_f(input1, input2, add)

share|improve this answer

answered Mar 28 at 21:30

Peter CollingridgePeter Collingridge

8,52733 gold badges3434 silver badges5454 bronze badges

answered Mar 28 at 21:30

Peter CollingridgePeter Collingridge

8,52733 gold badges3434 silver badges5454 bronze badges

answered Mar 28 at 21:30

Peter CollingridgePeter Collingridge

8,52733 gold badges3434 silver badges5454 bronze badges

0

Assuming the lists are always the right length (you can put a check for this), make your function recursive:

def add(a, b):

 if isinstance(a, list) and isinstance(b, list):
 for a_sub, b_sub in zip(a, b):
 return [add(a_sub, b_sub) for a_sub, b_sub in zip(a, b)]

 elif "NULL" not in [a, b]:
 return a + b

 elif "NULL" in [a, b]:
 return "NULL"

 else:
 raise ValueError("Wrong input shapes")

input1 = [[1, 2, "NULL"], [3, 4], [5, 6, 7, 8]]
input2 = [[9, 8, "NULL"], [7, 6], [5, 4, 3, 2]]

add(input1, input2)

Output:

[[10, 10, 'NULL'], [10, 10], [10, 10, 10, 10]]

share|improve this answer

answered Mar 28 at 21:29

dzangdzang

60933 silver badges1010 bronze badges

add a comment
 | 

0

Assuming the lists are always the right length (you can put a check for this), make your function recursive:

def add(a, b):

 if isinstance(a, list) and isinstance(b, list):
 for a_sub, b_sub in zip(a, b):
 return [add(a_sub, b_sub) for a_sub, b_sub in zip(a, b)]

 elif "NULL" not in [a, b]:
 return a + b

 elif "NULL" in [a, b]:
 return "NULL"

 else:
 raise ValueError("Wrong input shapes")

input1 = [[1, 2, "NULL"], [3, 4], [5, 6, 7, 8]]
input2 = [[9, 8, "NULL"], [7, 6], [5, 4, 3, 2]]

add(input1, input2)

Output:

[[10, 10, 'NULL'], [10, 10], [10, 10, 10, 10]]

share|improve this answer

answered Mar 28 at 21:29

dzangdzang

60933 silver badges1010 bronze badges

add a comment
 | 

Assuming the lists are always the right length (you can put a check for this), make your function recursive:

def add(a, b):

 if isinstance(a, list) and isinstance(b, list):
 for a_sub, b_sub in zip(a, b):
 return [add(a_sub, b_sub) for a_sub, b_sub in zip(a, b)]

 elif "NULL" not in [a, b]:
 return a + b

 elif "NULL" in [a, b]:
 return "NULL"

 else:
 raise ValueError("Wrong input shapes")

input1 = [[1, 2, "NULL"], [3, 4], [5, 6, 7, 8]]
input2 = [[9, 8, "NULL"], [7, 6], [5, 4, 3, 2]]

add(input1, input2)

Output:

[[10, 10, 'NULL'], [10, 10], [10, 10, 10, 10]]

share|improve this answer

answered Mar 28 at 21:29

dzangdzang

60933 silver badges1010 bronze badges

def add(a, b):

 if isinstance(a, list) and isinstance(b, list):
 for a_sub, b_sub in zip(a, b):
 return [add(a_sub, b_sub) for a_sub, b_sub in zip(a, b)]

 elif "NULL" not in [a, b]:
 return a + b

 elif "NULL" in [a, b]:
 return "NULL"

 else:
 raise ValueError("Wrong input shapes")

input1 = [[1, 2, "NULL"], [3, 4], [5, 6, 7, 8]]
input2 = [[9, 8, "NULL"], [7, 6], [5, 4, 3, 2]]

add(input1, input2)

[[10, 10, 'NULL'], [10, 10], [10, 10, 10, 10]]

share|improve this answer

answered Mar 28 at 21:29

dzangdzang

60933 silver badges1010 bronze badges

answered Mar 28 at 21:29

dzangdzang

60933 silver badges1010 bronze badges

answered Mar 28 at 21:29

dzangdzang

60933 silver badges1010 bronze badges