underpy 0.1

Functional helpers for Python

# UNDERPY

[](https://travis-ci.org/ramonski/underpy)
[](https://coveralls.io/r/ramonski/underpy?branch=develop)

```
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_ _ _ __ __| | ___ _ __ _ __ _ _
| | | | '_ \ / _` |/ _ \ '__| '_ \| | | |
| |_| | | | | (_| | __/ | | |_) | |_| |
\__,_|_| |_|\__,_|\___|_| | .__/ \__, |
|_| |___/

functional helpers for python
```


## Functions

``` python
alias(col, mapping)
Returns a collection of dictionaries with the keys renamed according to
the mapping

>>> libraries = [{"isbn": 1, "ed": 1}, {"isbn": 2, "ed": 2}]
>>> alias(libraries, {"ed": "edition"})
[{'edition': 1, 'isbn': 1}, {'edition': 2, 'isbn': 2}]

>>> alias({"a": 1}, {"a": "b"})
[{'b': 1}]

convert(value, converter)
Converts a value with a given converter function.

>>> convert("1", to_int)
1
>>> convert("0", to_int)
0
>>> convert("a", to_int)

fail(error)
Raises a RuntimeError with the given error Message

>>> fail("This failed badly")
Traceback (most recent call last):
...
RuntimeError: This failed badly

falsy(thing)
checks if a value is False or None

>>> falsy(0)
False
>>> falsy({})
False
>>> falsy([])
False
>>> falsy(None)
True
>>> falsy(False)
True

first(lst, n=None)
get the first element of a list

>>> lst = [1, 2, 3, 4, 5]
>>> first(lst)
1
>>> first(lst, 3)
[1, 2, 3]

is_dict(thing)
checks if an object is a dictionary type

>>> is_dict({})
True
>>> is_dict(dict())
True
>>> is_dict("{}")
False
>>> is_dict([])
False

is_digit(thing)
checks if an object is a digit

>>> is_digit(1)
True
>>> is_digit("1")
True
>>> is_digit("a")
False
>>> is_digit([])
False

is_list(thing)
checks if an object is a list type

>>> is_list([])
True
>>> is_list(list())
True
>>> is_list("[]")
False
>>> is_list({})
False

is_string(thing)
checks if an object is a string/unicode type

>>> is_string("")
True
>>> is_string(u"")
True
>>> is_string(str())
True
>>> is_string(unicode())
True
>>> is_string(1)
False

is_tuple(thing)
checks if an object is a tuple type

>>> is_tuple(())
True
>>> is_tuple(tuple())
True
>>> is_tuple("()")
False
>>> is_tuple([])
False

omit(dct, *keys)
Returns a copy of the dictionary filtered to omit the blacklisted keys
(or list of keys)

>>> omit({"name": "moe", "age": 50, "userid": "moe1"}, "userid", "age")
{'name': 'moe'}

pick(dct, *keys)
Returns a copy of the dictionary filtered to only have values for the
whitelisted keys (or list of valid keys)

>>> pick({"name": "moe", "age": 50, "userid": "moe1"}, "name", "age")
{'age': 50, 'name': 'moe'}

pluck(col, key, default=None)
Extracts a list of values from a collection of dictionaries

>>> stooges = [{"name": "moe", "age": 40},
... {"name": "larry", "age": 50},
... {"name": "curly", "age": 60}]
>>> pluck(stooges, "name")
['moe', 'larry', 'curly']

It only works with collections

>>> curly = stooges.pop()
>>> pluck(curly, "age")
Traceback (most recent call last):
...
RuntimeError: First argument must be a list or tuple

rename(dct, mapping)
Rename the keys of a dictionary with the given mapping

>>> rename({"a": 1, "BBB": 2}, {"a": "AAA"})
{'AAA': 1, 'BBB': 2}

to_int(thing)
coverts an object to int

>>> to_int("0")
0
>>> to_int(1)
1
>>> to_int("1")
1
>>> to_int("a")

to_list(thing)
converts an object to a list

>>> to_list(1)
[1]

>>> to_list([1,2,3])
[1, 2, 3]

>>> to_list(("a", "b", "c"))
['a', 'b', 'c']

>>> to_list(dict(a=1, b=2))
[{'a': 1, 'b': 2}]

to_string(thing)
coverts an object to string

>>> to_string(1)
'1'
>>> to_string([])
'[]'
>>> to_string(u"a")
'a'

def to_iso_date(thing):
converts an object to a iso date string

>>> to_iso_date("")
""
>>> dt = datetime.date.fromtimestamp(1387452665)
>>> to_iso_date(dt)
'2013-12-19'

truthy(thing)
checks if a value is True or not None

>>> truthy(0)
True
>>> truthy({})
True
>>> truthy([])
True
>>> truthy(None)
False
>>> truthy(False)
False
```


## Running the tests

```
python setup.py nosetests --with-doctest
```


## License

MIT