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# 30-seconds-of-python-code
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>Python implementation of 30-seconds-of-code.

**Note**:- This is in no way affiliated with the original [30-seconds-of-code](https://github.com/Chalarangelo/30-seconds-of-code/).


### chunk 

Chunks an array into smaller lists of a specified size.

Uses `range` to create a list of desired size. Then use `map` on this list and fill it with splices of `arr`.

```python 


from math import ceil


def chunk(arr, size):
    return list(
        map(lambda x: arr[x * size:x * size + size],
            list(range(0, ceil(len(arr) / size)))))

```

``` python
chunk([1,2,3,4,5],2) # [[1,2],[3,4],5]
```

### compact

Removes falsey values from a list.

Use `filter()` to filter out falsey values (False, None, 0, and "").

```python 


def compact(arr):
    return list(filter(lambda x: bool(x), arr))

```

``` python
compact([0, 1, False, 2, '', 3, 'a', 's', 34]); // [ 1, 2, 3, 'a', 's', 34 ]
```
### count_occurences

Counts the occurrences of a value in an list.

Uses the `reduce` functin from built-in module `functools` to increment a counter each time you encounter the specific value inside the list.

```python 


def count_occurences(arr, val):
    return reduce(
        (lambda x, y: x + 1 if y == val and type(y) == type(val) else x + 0),
        arr)

```

```python
count_occurrences([1, 1, 2, 1, 2, 3], 1) # 3
```
### count_vowels

Retuns `number` of vowels in provided `string`.

Use a regular expression to count the number of vowels `(A, E, I, O, U)` in a string.

```python 


import re


def count_vowels(str):
    return len(len(re.findall(r'[aeiou]', str, re.IGNORECASE)))

```

``` python
count_vowels('foobar') # 3
count_vowels('gym') # 0
```

### deep_flatten

Deep flattens a list.

Use recursion. Use `list.extend()` with an empty array (`result`) and the spread function to flatten a list. Recursively flatten each element that is a list.

```python 


def spread(arg):
    ret = []
    for i in arg:
        if isinstance(i, list):
            ret.extend(i)
        else:
            ret.append(i)
    return ret

 def deep_flatten(arr):
    result = []
    result.extend(spread(list(map(lambda x : deep(x) if type(x) == list else x,arr))))
    return result









```

```python
deep_flatten([1, [2], [[3], 4], 5]) # [1,2,3,4,5]
```

### difference

Returns the difference between two arrays.

Create a `set` from `b`, then use list comprehension to only keep values not contained in `b`

```python 


def difference(a, b):
    b = set(b)
    return [item for item in a if item not in b]

```
``` python
difference([1, 2, 3], [1, 2, 4]) # [3]
```
### gcd

Calculates the greatest common divisor between two or more numbers/lists.

The `helperGcdfunction` uses recursion. Base case is when `y` equals `0`. In this case, return `x`. Otherwise, return the GCD of `y` and the remainder of the division `x/y`.

Uses the reduce function from the inbuilt module `functools`. Also defines a method `spread` for javascript like spreading of lists.

```python 


from functools import reduce


def spread(arg):
    ret = []
    for i in arg:
        if isinstance(i, list):
            ret.extend(i)
        else:
            ret.append(i)
    return ret


def gcd(*args):
    numbers = []
    numbers.extend(spread(list(args)))

    def _gcd(x, y):
        return x if not y else gcd(y, x % y)

    return reduce((lambda x, y: _gcd(x, y)), numbers)

```


``` python
gcd(8,36) # 4
```
### lcm 

Returns the least common multiple of two or more numbers.

Use the `greatest common divisor (GCD)` formula and the fact that `lcm(x,y) = x * y / gcd(x,y)` to determine the least common multiple. The GCD formula uses recursion.

Uses `reduce` function from the inbuilt module `functools`. Also defines a method `spread` for javascript like spreading of lists.

```python 


from functools import reduce


def spread(arg):
    ret = []
    for i in arg:
        if isinstance(i, list):
            ret.extend(i)
        else:
            ret.append(i)
    return ret


def lcm(*args):
    numbers = []
    numbers.extend(spread(list(args)))

    def _gcd(x, y):
        return x if not y else gcd(y, x % y)

    def _lcm(x, y):
        return x * y / _gcd(x, y)

    return reduce((lambda x, y: _lcm(x, y)), numbers)

```


``` python
lcm(12, 7) # 84
lcm([1, 3, 4], 5) # 60
```
### max_n

Returns the `n` maximum elements from the provided list. If `n` is greater than or equal to the provided list's length, then return the original list(sorted in descending order).

Use `list.sort()` combined with the `deepcopy` function from the inbuilt `copy` module to create a shallow clone of the list and sort it in ascending order and then use `list.reverse()` reverse it to make it descending order. Use `[:n]` to get the specified number of elements. Omit the second argument, `n`, to get a one-element array

```python 


from copy import deepcopy


def max_n(arr, n=1):
    numbers = deepcopy(arr)
    numbers.sort()
    numbers.reverse()
    return numbers[:n]

```

```python
max_n([1, 2, 3]) # [3]
max_n([1, 2, 3], 2) # [3,2]
```
### min_n

Returns the `n` minimum elements from the provided list. If `n` is greater than or equal to the provided list's length, then return the original list(sorted in ascending order).

Use `list.sort()` combined with the `deepcopy` function from the inbuilt `copy` module to create a shallow clone of the list and sort it in ascending order. Use `[:n]` to get the specified number of elements. Omit the second argument, `n`, to get a one-element array

```python 


from copy import deepcopy


def min_n(arr, n=1):
    numbers = deepcopy(arr)
    numbers.sort()
    return numbers[:n]

```

```python
min_n([1, 2, 3]) # [1]
min_n([1, 2, 3], 2) # [1,2]
```
### shuffle

Randomizes the order of the values of an list, returning a new list.

Uses the [Fisher-Yates algorithm](https://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle) to reorder the elements of the list.

```python 


from copy import deepcopy
from random import randint


def shuffle(arr):
    temp_arr = deepcopy(arr)
    m = len(temp_arr)
    while(m):
        m -= 1
        i = randint(0, m)
        temp_arr[m], temp_arr[i] = temp_arr[i], temp_arr[m]
    return temp_arr

```

``` python
foo = [1,2,3]
shuffle(foo) # [2,3,1] , foo = [1,2,3]
```
### spread

Implements javascript's spread syntax as a function. Flattens the list(non-deep) and returns an list.

```python 


def spread(arg):
    ret = []
    for i in arg:
        if isinstance(i, list):
            ret.extend(i)
        else:
            ret.append(i)
    return ret

```


```python
spread([1,2,3,[4,5,6],[7],8,9]) # [1,2,3,4,5,6,7,8,9]
```
### zip

Creates a list of elements, grouped based on the position in the original lists.

Use `max` combined with `list comprehension` to get the length of the longest list in the arguments. Loops for `max_length` times grouping elements. If lengths of `lists` vary `fill_value` is used. By default `fill_value` is `None`.

```python 


def zip(*args, fillvalue=None):
    max_length = max([len(arr) for arr in args])
    result = []
    for i in range(max_length):
        result.append([args[k][i] if i < len(args[k])
                       else None for k in range(len(args))])
    return result

```

``` python
zip(['a', 'b'], [1, 2], [True, False]); // [['a', 1, True], ['b', 2, False]]
zip(['a'], [1, 2], [True, False]); // [['a', 1, True], [None, 2, False]]
zip(['a'], [1, 2], [True, False], fill_value = '_'); // [['a', 1, True], ['_', 2, False]]
```

## Credits

*Icons made by [Smashicons](https://www.flaticon.com/authors/smashicons) from [www.flaticon.com](https://www.flaticon.com/) is licensed by [CC 3.0 BY](http://creativecommons.org/licenses/by/3.0/).*