CODEWITHSUNDEEP
pythonpython-3.xzippython-itertoolschain
Chris
Chris

Reputation: 387

How to create a dictionary with itertools by combining a tuple and static string

Currently I have an iterator that produces: 

(0, 10), (10, 20), (20, 30), (30, 40), (40, 50), (50, 56), (56, None)

What I'm looking to produce: 

[["current": "0", "next":"10", "default": "value"], ["current": "10", "next":"20", "default": "value"]],

What I have so far: 

('default', (0, 10)), ('default', (10, 20)), ('default', (20, 30)), ('default', (30, 40)), ('default', (40, 50)), ('default', (50, 56)), ('default', (56, None))

What changes can I make to produce dictionaries from my list of tuples?

Here is the code to reproduce what I have:

start = 0
end = 56
step = 10

part = itertools.islice(range(end), start, end, step)
end = [end]
iterables = itertools.chain(part, end)

items, nexts = itertools.tee(iterables)
# items = [0, 10, 20, 30, 40, 50, 56]
nexts = itertools.chain(itertools.islice(nexts, 1, None), [None])
# next = [10, 20, 30, 40, 50, 56, None]
results = itertools.zip_longest(items, nexts)
# [(0, 10), (10, 20), (20, 30), (30, 40), (40, 50), (50, 56), (56, None)]

static = "default"

result = zip(itertools.repeat(static),results)
print(list(result))

Note, I would love to only use itertools to complete this if possible, I really don't want to hold an entire list of dictionaries in memory.

Upvotes: 2

Views: 1291

Answers (2)

Stephen Rauch
Stephen Rauch

Reputation: 49804

From your sequence of tuples, you can do a list comprehension (or a generator expression) like:

[{"current": str(x), "next": str(y), "default": "value"} for x, y in data]

Test Code:

data = ((0, 10), (10, 20), (20, 30), (30, 40), (40, 50), (50, 56), (56, None))

print([{"current": str(x), "next": str(y), "default": "value"} for x, y in data])

Results:

[
{'current': '0', 'next': '10', 'default': 'value'}, 
{'current': '10', 'next': '20', 'default': 'value'}, 
{'current': '20', 'next': '30', 'default': 'value'}, 
{'current': '30', 'next': '40', 'default': 'value'}, 
{'current': '40', 'next': '50', 'default': 'value'}, 
{'current': '50', 'next': '56', 'default': 'value'},
{'current': '56', 'next': 'None', 'default': 'value'}
]

Upvotes: 1

Selcuk
Selcuk

Reputation: 59228

Writing your own generator function could be more readable in such cases. For example:

def items():
    start = 0
    end = 56
    step = 10

    while True:
        d = {"current": start,
             "next": start + step if start + step < end else end if start < end else None,
             "default": "value"}
        yield d
        if start >= end:
            break
        else:
            start += step
            if start > end:
                start = end

print(list(items()))

output:

[{'current': 0, 'next': 10, 'default': 'value'}, 
 {'current': 10, 'next': 20, 'default': 'value'}, 
 {'current': 20, 'next': 30, 'default': 'value'}, 
 {'current': 30, 'next': 40, 'default': 'value'}, 
 {'current': 40, 'next': 50, 'default': 'value'}, 
 {'current': 50,'next': 56, 'default': 'value'}, 
 {'current': 56, 'next': None, 'default': 'value'}]

Upvotes: 1

Related Questions