In Python, a list is a dynamic array. You can create one like this:
lst = [] # Declares an empty list named lst
Or you can fill it with items:
lst = [1,2,3]
You can add items using "append":
lst.append('a')
You can iterate over elements of the list using the for loop:
for item in lst:
# Do something with item
Or, if you'd like to keep track of the current index:
for idx, item in enumerate(lst):
# idx is the current idx, while item is lst[idx]
To remove elements, you can use the del command or the remove function as in:
del lst[0] # Deletes the first item
lst.remove(x) # Removes the first occurence of x in the list
Note, though, that one cannot iterate over the list and modify it at the same time; to do that, you should instead iterate over a slice of the list (which is basically a copy of the list). As in:
for item in lst[:]: # Notice the [:] which makes a slice
# Now we can modify lst, since we are iterating over a copy of it
you can declare a Numpy array dynamically for 1 dimension as shown below:
import numpy as np
n = 2
new_table = np.empty(shape=[n,1])
new_table[0,0] = 2
new_table[1,0] = 3
print(new_table)
The above example assumes we know we need to have 1 column but we want to allocate the number of rows dynamically (in this case the number or rows required is equal to 2)
output is shown below:
[[2.] [3.]]
In python, A dynamic array is an 'array' from the array module. E.g.
from array import array
x = array('d') #'d' denotes an array of type double
x.append(1.1)
x.append(2.2)
x.pop() # returns 2.2
This datatype is essentially a cross between the built-in 'list' type and the numpy 'ndarray' type. Like an ndarray, elements in arrays are C types, specified at initialization. They are not pointers to python objects; this may help avoid some misuse and semantic errors, and modestly improves performance.
However, this datatype has essentially the same methods as a python list, barring a few string & file conversion methods. It lacks all the extra numerical functionality of an ndarray.
See https://docs.python.org/2/library/array.html for details.
Here's a great method I recently found on a different stack overflow post regarding multi-dimensional arrays, but the answer works beautifully for single dimensional arrays as well:
# Create an 8 x 5 matrix of 0's:
w, h = 8, 5;
MyMatrix = [ [0 for x in range( w )] for y in range( h ) ]
# Create an array of objects:
MyList = [ {} for x in range( n ) ]
I love this because you can specify the contents and size dynamically, in one line!
One more for the road:
# Dynamic content initialization:
MyFunkyArray = [ x * a + b for x in range ( n ) ]
Source: Stackoverflow.com