# Python find largest N (top N) or smallest N items

Python examples to find the largest (or the smallest) N elements from a collection of elements using nlargest() and nsmallest() functions from heapq library.

## 1. Using heapq module’s nlargest() and nsmallest()

Python `heapq` module can be used to find N largest or smallest items from collections. It has two functions to help with –

1. `nlargest()`
2. `nsmallest()`

#### 1.1. Find items in simple iterables

```>>> import heapq

>>> nums = [1, 8, 2, 23, 7, -4, 18, 23, 42, 37, 2]

print(heapq.nlargest(3, nums))
>>> [42, 37, 23]

print(heapq.nsmallest(3, nums))
>>> [-4, 1, 2]
```

#### 1.2. Find items in complex iterables

```>>> portfolio =
[
{'name': 'IBM', 'shares': 100, 'price': 91.1},
{'name': 'AAPL', 'shares': 50, 'price': 543.22},
{'name': 'FB', 'shares': 200, 'price': 21.09},
{'name': 'HPQ', 'shares': 35, 'price': 31.75},
{'name': 'YHOO', 'shares': 45, 'price': 16.35},
{'name': 'ACME', 'shares': 75, 'price': 115.65}
]

>>> cheap = heapq.nsmallest(3, portfolio, key=lambda s: s['price'])
>> cheap
>>> [
{'price': 16.35, 'name': 'YHOO', 'shares': 45},
{'price': 21.09, 'name': 'FB', 'shares': 200},
{'price': 31.75, 'name': 'HPQ', 'shares': 35}
]

>>> expensive = heapq.nlargest(3, portfolio, key=lambda s: s['price'])
>>> expensive
>>> [
{'price': 543.22, 'name': 'AAPL', 'shares': 50},
{'price': 115.65, 'name': 'ACME', 'shares': 75},
{'price': 91.1, 'name': 'IBM', 'shares': 100}
]
```
If you are simply trying to find the single smallest or largest item (`N=1`), it is faster to use `min()` and `max()` functions.

Happy Learning !!

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