﻿ Python: Return every element that exists in any of the two given lists once, after applying function to each element of both - w3resource

# Python: Return every element that exists in any of the two given lists once, after applying function to each element of both

## Python List: Exercise - 228 with Solution

Write a Python program to get every element that exists in any of the two given lists once, after applying the provided function to each element of both.

• Create a set by applying fn to each element in x.
• Use a list comprehension in combination with fn on y to only keep values not contained in the previously created set, _x.
• Finally, create a set from the previous result and x and transform it into a list.

Sample Solution:

Python Code:

``````def union_by_el(x, y, fn):
_x = set(map(fn, x))
return list(set(x + [item for item in y if fn(item) not in _x]))
from math import floor
print(union_by_el([4.1], [2.2, 4.3], floor))
```
```

Sample Output:

```[2.2, 4.1]
```

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## Python: Tips of the Day

Decapitalizes the first letter of a string:

Example:

```def tips_decapitalize(s, upper_rest=False):
return s[:1].lower() + (s[1:].upper() if upper_rest else s[1:])
print(tips_decapitalize('PythonTips'))
print(tips_decapitalize('PythonTips', True))
```

Output:

```pythonTips
pYTHONTIPS
```

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