Maps in Elm

Based on the provided input, the target language is “Python”. Below is the translated Go code and explanation in Python, formatted in Markdown suitable for Hugo.

Maps are Python’s built-in associative data type (sometimes called dictionaries in other languages).

To create an empty dictionary, you can use {} or dict().

m = {}

Set key/value pairs using typical name[key] = val syntax.

m["k1"] = 7
m["k2"] = 13

Printing a dictionary with print will show all of its key/value pairs.

print("map:", m)

Get a value for a key with name[key].

v1 = m["k1"]
print("v1:", v1)

If the key doesn’t exist, a KeyError will be raised. Alternatively, you can use the get method which returns None (or a specified value) if the key is not found.

v3 = m.get("k3", 0)
print("v3:", v3)

The built-in len function returns the number of key/value pairs when called on a dictionary.

print("len:", len(m))

The built-in del statement removes key/value pairs from a dictionary.

del m["k2"]
print("map:", m)

To remove all key/value pairs from a dictionary, use the clear method.

m.clear()
print("map:", m)

The optional second return value when getting a value from a dictionary indicates if the key was present in the dictionary. This can be used to disambiguate between missing keys and keys with zero values like 0 or "".

prs = "k2" in m
print("prs:", prs)

You can also declare and initialize a new dictionary in the same line with this syntax.

n = {"foo": 1, "bar": 2}
print("map:", n)

Note that dictionaries appear in the form {'k': 'v', 'k': 'v'} when printed with print.

$ python3 maps.py
map: {'k1': 7, 'k2': 13}
v1: 7
v3: 0
len: 2
map: {'k1': 7}
map: {}
prs: False
map: {'foo': 1, 'bar': 2}

Next example: Functions.