November 2017 • Programmer

Python: how to save a dictionary with objects to JSON

Leave a Comment / Nikita / 22.11.2017

Each object’s class to be stored in JSON in a convenient for viewing way must have the __repr__ function, which returns the text representation of the object.

class TestObj:

    def __init__(self, x, y):
        self.__x = x
        self.__y = y

    def __repr__(self):
        return "TestObj({x},{y})".format(x = self.__x, y = self.__y)

class TestObj:

def __init__(self, x, y):

self.__x = x

self.__y = y

def __repr__(self):

return "TestObj({x},{y})".format(x = self.__x, y = self.__y)

The dictionary with objects:

datadict = {"group": {"Object1": TestObj(10,22), "Object2": TestObj(36,74)}}

1	datadict = {"group": {"Object1": TestObj(10,22), "Object2": TestObj(36,74)}}

Saving the dictionary to JSON:

with open("c:/file.json", "w", encoding="utf-8") as file:
    import pprint
    pprint.pprint(datadict, indent=4, stream=file)
    file.close()

with open("c:/file.json", "w", encoding="utf-8") as file:

import pprint

pprint.pprint(datadict, indent=4, stream=file)

file.close()

Python: how to enclose a tuple in a tuple

Leave a Comment / Nikita / 08.11.2017

Tuples in python can be nested.

If simply add one tuple to another through the concatenation operation “+”, python will merge the values of the tuples:

a = ((1, 2), (3, 4))
print(a)    # ((1, 2), (3, 4))

b = (5, 6)
print(b)    # (5, 6)

a += b
print(a)    # ((1, 2), (3, 4), 5, 6)

a = ((1, 2), (3, 4))

print(a) # ((1, 2), (3, 4))

b = (5, 6)

print(b) # (5, 6)

a += b

print(a) # ((1, 2), (3, 4), 5, 6)

In order an added tuple to become nested, put a comma “,” after an added tuple:

a += b,
print(a)    # ((1, 2), (3, 4), (5, 6))

1 2	a += b, print(a) # ((1, 2), (3, 4), (5, 6))

Python: How to find the polygon center coordinates

Leave a Comment / Nikita / 08.11.2017

Obtaining the “centroid” – convex polygon central point coordinates, from polygons points (vertices) coordinates:

def centroid(vertexes):
     _x_list = [vertex [0] for vertex in vertexes]
     _y_list = [vertex [1] for vertex in vertexes]
     _len = len(vertexes)
     _x = sum(_x_list) / _len
     _y = sum(_y_list) / _len
     return(_x, _y)

def centroid(vertexes):

_x_list = [vertex [0] for vertex in vertexes]

_y_list = [vertex [1] for vertex in vertexes]

_len = len(vertexes)

_x = sum(_x_list) / _len

_y = sum(_y_list) / _len

return(_x, _y)

The input function parameter is a tuple with coordinates of the polygon points. The function returns a tuple with the centroid coordinates:

polygon_data = ((0, 0), (1, 0), (1, 1), (0, 1))
print(centroid(polygon_data)) # (0.5, 0.5)

1 2	polygon_data = ((0, 0), (1, 0), (1, 1), (0, 1)) print(centroid(polygon_data)) # (0.5, 0.5)