Search in a nested list of a dictionary

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1
down vote

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I have a dictionary structured as a_1: [((b_11,c_11),d_11), ((b_12, c_12), d_12), ...], a_2: [...], ....

I want to extract the maximum abs(c) among all the possible c values. Currently I'm doing this throught two for loops. One for each a, and other for each of set b,c,d.

elements = 
 0: [((0, -4), 1)], 
 1: [((1, -5), 1), ((0, -4), 1)],
 2: [((2, -3), 1)],
 3: [((3, -2), 1), ((0, -5), 1)],
 

max_c = 0

for a in list(elements):
 for (b, c), d in elements[a]:
 max_c = max(max_c, abs(c))

Is there any way to do this without the for loops? and if it is, is it pythonic? or I should keep this way because it's more understandable?

Thanks in advance.

edited 3 hours ago

asked 3 hours ago

Xbel

235

New contributor

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up vote
1
down vote

favorite

I have a dictionary structured as a_1: [((b_11,c_11),d_11), ((b_12, c_12), d_12), ...], a_2: [...], ....

I want to extract the maximum abs(c) among all the possible c values. Currently I'm doing this throught two for loops. One for each a, and other for each of set b,c,d.

elements = 
 0: [((0, -4), 1)], 
 1: [((1, -5), 1), ((0, -4), 1)],
 2: [((2, -3), 1)],
 3: [((3, -2), 1), ((0, -5), 1)],
 

max_c = 0

for a in list(elements):
 for (b, c), d in elements[a]:
 max_c = max(max_c, abs(c))

Is there any way to do this without the for loops? and if it is, is it pythonic? or I should keep this way because it's more understandable?

Thanks in advance.

edited 3 hours ago

asked 3 hours ago

Xbel

235

New contributor

add a commentÂ |Â

up vote
1
down vote

favorite

I have a dictionary structured as a_1: [((b_11,c_11),d_11), ((b_12, c_12), d_12), ...], a_2: [...], ....

I want to extract the maximum abs(c) among all the possible c values. Currently I'm doing this throught two for loops. One for each a, and other for each of set b,c,d.

elements = 
 0: [((0, -4), 1)], 
 1: [((1, -5), 1), ((0, -4), 1)],
 2: [((2, -3), 1)],
 3: [((3, -2), 1), ((0, -5), 1)],
 

max_c = 0

for a in list(elements):
 for (b, c), d in elements[a]:
 max_c = max(max_c, abs(c))

Is there any way to do this without the for loops? and if it is, is it pythonic? or I should keep this way because it's more understandable?

Thanks in advance.

edited 3 hours ago

asked 3 hours ago

Xbel

235

New contributor

I have a dictionary structured as a_1: [((b_11,c_11),d_11), ((b_12, c_12), d_12), ...], a_2: [...], ....

I want to extract the maximum abs(c) among all the possible c values. Currently I'm doing this throught two for loops. One for each a, and other for each of set b,c,d.

elements = 
 0: [((0, -4), 1)], 
 1: [((1, -5), 1), ((0, -4), 1)],
 2: [((2, -3), 1)],
 3: [((3, -2), 1), ((0, -5), 1)],
 

max_c = 0

for a in list(elements):
 for (b, c), d in elements[a]:
 max_c = max(max_c, abs(c))

Is there any way to do this without the for loops? and if it is, is it pythonic? or I should keep this way because it's more understandable?

Thanks in advance.

python dictionary

edited 3 hours ago

asked 3 hours ago

Xbel

235

New contributor

edited 3 hours ago

asked 3 hours ago

Xbel

235

New contributor

edited 3 hours ago

asked 3 hours ago

Xbel

235

New contributor

asked 3 hours ago

Xbel

235

asked 3 hours ago

Xbel

235

New contributor

Xbel is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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2 Answers
2

active

oldest

votes

up vote
2
down vote

If you were to extract all abs(c) into a list, you could use max over that list.

Fortunately, this is easy using your loops and a list-comprehension:

Cs = [
 abs(value)
 for collection in elements.values()
 for (_, value), _ in collection
]
max_c = max(Cs)

Note the use of elements.values() instead of extracting the values manually (elements[a]) and the use of _ as a throwaway variable.

Now max works on any iterable, meaning we don't even have to build a temporary list and can feed it a generator-expression:

max_c = max(
 abs(value)
 for collection in elements.values()
 for (_, value), _ in collection
)

answered 30 mins ago

Mathias Ettinger

22.5k33077

add a commentÂ |Â

up vote
2
down vote

When you are looping over the keys a and values elements[a] of a dictionary, use the items method to loop over both at the same time:
```
for a, value in elements.items():
 for (b, c), d in value:
```
(If I knew what these values represented, I would pick a better name than value.)

The code here doesn't use the keys, it only uses the values. So use the values method instead:
```
for value in elements.values():
 for (b, c), d in value:
```

The code doesn't use b or d either. It is conventional to use the name _ for unused variables:
```
for (_, c), _ in value:
```

A double iteration over some lists and then over the elements of those lists can be combined into a single iteration using itertools.chain.from_iterable:
```
from itertools import chain
for (_, c), _ in chain.from_iterable(elements.values()):
```

The repeated calls to max can become a single call taking a generator expression:

values = chain.from_iterable(elements.values())
max_abs_c = max(abs(c) for (_, c), _ in values)

It's common to worry whether code is "Pythonic" but it is better to think in terms of general principles (clarity, simplicity, maintainability, testability, usability, efficiency, etc.) that apply to code in any language.

edited 24 mins ago

answered 29 mins ago

Gareth Rees

43.5k396175

add a commentÂ |Â

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2 Answers
2

active

oldest

votes

2 Answers
2

active

oldest

votes

up vote
2
down vote

If you were to extract all abs(c) into a list, you could use max over that list.

Fortunately, this is easy using your loops and a list-comprehension:

Cs = [
 abs(value)
 for collection in elements.values()
 for (_, value), _ in collection
]
max_c = max(Cs)

Note the use of elements.values() instead of extracting the values manually (elements[a]) and the use of _ as a throwaway variable.

Now max works on any iterable, meaning we don't even have to build a temporary list and can feed it a generator-expression:

max_c = max(
 abs(value)
 for collection in elements.values()
 for (_, value), _ in collection
)

answered 30 mins ago

Mathias Ettinger

22.5k33077

add a commentÂ |Â

up vote
2
down vote

If you were to extract all abs(c) into a list, you could use max over that list.

Fortunately, this is easy using your loops and a list-comprehension:

Cs = [
 abs(value)
 for collection in elements.values()
 for (_, value), _ in collection
]
max_c = max(Cs)

Note the use of elements.values() instead of extracting the values manually (elements[a]) and the use of _ as a throwaway variable.

Now max works on any iterable, meaning we don't even have to build a temporary list and can feed it a generator-expression:

max_c = max(
 abs(value)
 for collection in elements.values()
 for (_, value), _ in collection
)

answered 30 mins ago

Mathias Ettinger

22.5k33077

add a commentÂ |Â

up vote
2
down vote

If you were to extract all abs(c) into a list, you could use max over that list.

Fortunately, this is easy using your loops and a list-comprehension:

Cs = [
 abs(value)
 for collection in elements.values()
 for (_, value), _ in collection
]
max_c = max(Cs)

Note the use of elements.values() instead of extracting the values manually (elements[a]) and the use of _ as a throwaway variable.

Now max works on any iterable, meaning we don't even have to build a temporary list and can feed it a generator-expression:

max_c = max(
 abs(value)
 for collection in elements.values()
 for (_, value), _ in collection
)

answered 30 mins ago

Mathias Ettinger

22.5k33077

If you were to extract all abs(c) into a list, you could use max over that list.

Fortunately, this is easy using your loops and a list-comprehension:

Cs = [
 abs(value)
 for collection in elements.values()
 for (_, value), _ in collection
]
max_c = max(Cs)

Note the use of elements.values() instead of extracting the values manually (elements[a]) and the use of _ as a throwaway variable.

Now max works on any iterable, meaning we don't even have to build a temporary list and can feed it a generator-expression:

max_c = max(
 abs(value)
 for collection in elements.values()
 for (_, value), _ in collection
)

answered 30 mins ago

Mathias Ettinger

22.5k33077

answered 30 mins ago

Mathias Ettinger

22.5k33077

answered 30 mins ago

Mathias Ettinger

22.5k33077

answered 30 mins ago

Mathias Ettinger

22.5k33077

add a commentÂ |Â

up vote
2
down vote

When you are looping over the keys a and values elements[a] of a dictionary, use the items method to loop over both at the same time:
```
for a, value in elements.items():
 for (b, c), d in value:
```
(If I knew what these values represented, I would pick a better name than value.)

The code here doesn't use the keys, it only uses the values. So use the values method instead:
```
for value in elements.values():
 for (b, c), d in value:
```

The code doesn't use b or d either. It is conventional to use the name _ for unused variables:
```
for (_, c), _ in value:
```

A double iteration over some lists and then over the elements of those lists can be combined into a single iteration using itertools.chain.from_iterable:
```
from itertools import chain
for (_, c), _ in chain.from_iterable(elements.values()):
```

The repeated calls to max can become a single call taking a generator expression:

values = chain.from_iterable(elements.values())
max_abs_c = max(abs(c) for (_, c), _ in values)

It's common to worry whether code is "Pythonic" but it is better to think in terms of general principles (clarity, simplicity, maintainability, testability, usability, efficiency, etc.) that apply to code in any language.

edited 24 mins ago

answered 29 mins ago

Gareth Rees

43.5k396175

add a commentÂ |Â

up vote
2
down vote

When you are looping over the keys a and values elements[a] of a dictionary, use the items method to loop over both at the same time:
```
for a, value in elements.items():
 for (b, c), d in value:
```
(If I knew what these values represented, I would pick a better name than value.)

The code here doesn't use the keys, it only uses the values. So use the values method instead:
```
for value in elements.values():
 for (b, c), d in value:
```

The code doesn't use b or d either. It is conventional to use the name _ for unused variables:
```
for (_, c), _ in value:
```

A double iteration over some lists and then over the elements of those lists can be combined into a single iteration using itertools.chain.from_iterable:
```
from itertools import chain
for (_, c), _ in chain.from_iterable(elements.values()):
```

The repeated calls to max can become a single call taking a generator expression:

values = chain.from_iterable(elements.values())
max_abs_c = max(abs(c) for (_, c), _ in values)

It's common to worry whether code is "Pythonic" but it is better to think in terms of general principles (clarity, simplicity, maintainability, testability, usability, efficiency, etc.) that apply to code in any language.

edited 24 mins ago

answered 29 mins ago

Gareth Rees

43.5k396175

add a commentÂ |Â

up vote
2
down vote

When you are looping over the keys a and values elements[a] of a dictionary, use the items method to loop over both at the same time:
```
for a, value in elements.items():
 for (b, c), d in value:
```
(If I knew what these values represented, I would pick a better name than value.)

The code here doesn't use the keys, it only uses the values. So use the values method instead:
```
for value in elements.values():
 for (b, c), d in value:
```

The code doesn't use b or d either. It is conventional to use the name _ for unused variables:
```
for (_, c), _ in value:
```

A double iteration over some lists and then over the elements of those lists can be combined into a single iteration using itertools.chain.from_iterable:
```
from itertools import chain
for (_, c), _ in chain.from_iterable(elements.values()):
```

The repeated calls to max can become a single call taking a generator expression:

values = chain.from_iterable(elements.values())
max_abs_c = max(abs(c) for (_, c), _ in values)

It's common to worry whether code is "Pythonic" but it is better to think in terms of general principles (clarity, simplicity, maintainability, testability, usability, efficiency, etc.) that apply to code in any language.

edited 24 mins ago

answered 29 mins ago

Gareth Rees

43.5k396175

When you are looping over the keys a and values elements[a] of a dictionary, use the items method to loop over both at the same time:
```
for a, value in elements.items():
 for (b, c), d in value:
```
(If I knew what these values represented, I would pick a better name than value.)

The code here doesn't use the keys, it only uses the values. So use the values method instead:
```
for value in elements.values():
 for (b, c), d in value:
```

The code doesn't use b or d either. It is conventional to use the name _ for unused variables:
```
for (_, c), _ in value:
```

A double iteration over some lists and then over the elements of those lists can be combined into a single iteration using itertools.chain.from_iterable:
```
from itertools import chain
for (_, c), _ in chain.from_iterable(elements.values()):
```

The repeated calls to max can become a single call taking a generator expression:

values = chain.from_iterable(elements.values())
max_abs_c = max(abs(c) for (_, c), _ in values)

It's common to worry whether code is "Pythonic" but it is better to think in terms of general principles (clarity, simplicity, maintainability, testability, usability, efficiency, etc.) that apply to code in any language.

edited 24 mins ago

answered 29 mins ago

Gareth Rees

43.5k396175

edited 24 mins ago

answered 29 mins ago

Gareth Rees

43.5k396175

answered 29 mins ago

Gareth Rees

43.5k396175

answered 29 mins ago

Gareth Rees

43.5k396175

add a commentÂ |Â

Xbel is a new contributor. Be nice, and check out our Code of Conduct.

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