Python nested loop iterate a list in list

Question

Hi I'm trying to become a better programmer with short and clean code. I'm trying to loop through a list in a list and change it to dictionary inside a list here is my code right now please show me if there is anyway to achieve is with shorter lines of code.

1st I need to loop through the list to change the miliseconds to date and then I need to loop through and add keys to the list so that I know what each value is.

import datetime

formatter = ['Date', 'Open', 'Close', 'High', 'Low', 'Volume']
list = [[1364770800000, 93.2, 93.033, 93.29, 92.9, 116.0018], [1364774400000, 93.25, 93.1, 100, 93.03, 345.58388931]]

print(list)

def mili_to_date(d):
    d /= 1000.0
    return datetime.date.fromtimestamp(d).strftime('%Y-%m-%d')


for i, row in enumerate(list):
    for index, column in enumerate(row):
        if index == 0:
            list[i][0] = mili_to_date(column)
        else:
            pass

for i, row in enumerate(list):
    list[i] = {}
    for index, column in enumerate(row):
        list[i][candles_formatter[index]] = column

print(list)

Patrick Artner · Accepted Answer · 2018-03-03 15:07:19Z

2

To be(-come) a better programmer:

document your functions
embrace error handling and think about which errors might happen for creative input
use list/dict comprehensions
do not use names of built-in or datatypes like set/list/dict/tuple/... as variable names
leverage the power of built-ins - like zip():

import datetime as dt
from pprint import pprint # just for formatting

def mili_to_date(d):
    """Uses a time in milliseconds since 1970.1.1 (unix time) and creates a string date"""

    d /= 1000.0
    return dt.date.fromtimestamp(d).strftime('%Y-%m-%d')

def toDict(lis):
    """Secret method to map inner list to keys. Shhh - dont tell no one nothing.

    TODO: Also, when time, implement tests to assure length-equality between mapping and 
    input as well as some error handling if the 'Date' is not a number or something is 
    None. Lenght euqality is important as zip will only work for as much as the shorter
    list is long. If its shorter then length of formatter, some dict keys will not occure.
    Look at itertools.zip_longest() for a zip that fills the shorter lists with defaults."""

    formatter = ['Date', 'Open', 'Close', 'High', 'Low', 'Volume']
    z = zip(formatter,lis) 
    return { key: mili_to_date(val) if key == 'Date' else val for key,val in z}

if __name__ == "__main__": 
    # make me a dictionary
    li = [[1364770800000, 93.2, 93.033, 93.29, 92.9, 116.0018],
          [1364774400000, 93.25, 93.1, 100, 93.03, 345.58388931]]
    L = [toDict(x) for x in li] 
    pprint(L)

Output:

[{'Close': 93.033,
  'Date': '2013-04-01',
  'High': 93.29,
  'Low': 92.9,
  'Open': 93.2,
  'Volume': 116.0018},
 {'Close': 93.1,
  'Date': '2013-04-01',
  'High': 100,
  'Low': 93.03,
  'Open': 93.25,
  'Volume': 345.58388931}]

edited Mar 3, 2018 at 15:07

answered Mar 3, 2018 at 12:54

Patrick Artner

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2 Comments

Man Nguyen Over a year ago

Thank you very much for replying. So in your code above putting brackets around key,value would that means we now have tuples in side a dict?

Patrick Artner Over a year ago

@MightAsWell No, that simply means I screwed up and returned a list of sets of tuples instead of what you wanted. Fixed it, thanks for the pointer :) - So last advice: triple-check your wanted outputs and what you deliver ;)

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