23 lines
554 B
Markdown
23 lines
554 B
Markdown
---
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title: frequencies
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tags: list,intermediate
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---
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Returns a dictionary with the unique values of a list as keys and their frequencies as the values.
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Use a `for` loop to populate a dictionary, `f`, with the unique values in `lst` as keys, adding to existing keys every time the same value is encountered.
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```py
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from functools import reduce
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def frequencies(lst):
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f = {}
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for x in lst:
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f[x] = f[x] + 1 if x in f else 1
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return f
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```
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```py
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frequencies(['a', 'b', 'a', 'c', 'a', 'a', 'b']) # { 'a': 4, 'b': 2, 'c': 1 }
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```
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