## 7/07/2020

### extract year, month, day from file on Ubuntu, python example

...
import os, time
date_created_obj = time.localtime(os.path.getctime(full_path))
print('Year: {:4d}'.format(date_created_obj.tm_year)) # Year: 2020
print('Month: {:2d}'.format(date_created_obj.tm_mon)) # Month: 2
print('Day: {:2d}'.format(date_created_obj.tm_mday)) # Day: 10

...

## 7/06/2020

### how to merge two csr_matrix, example python source code

let's see the code.

..
from scipy.sparse import csr_matrix
import numpy as np

#first matrix
row = np.array([0, 0, 1, 2, 2, 2])
col = np.array([0, 2, 2, 0, 1, 2])
data = np.array([1, 1, 1, 1, 1, 1])
mtx = csr_matrix((data, (row, col)), shape=(3, 3))

#second matrix
row = np.array([0, 0, 1, 2, 2, 2])
col = np.array([0, 1, 2, 0, 1, 2])
data = np.array([1, 1, 1, 1, 1, 1])
mtx2 = csr_matrix((data, (row, col)), shape=(3, 3))

#merge two matrix
mtx3 = merge_two_csr_mtx(mtx, mtx2)

#check
print('1st\n',mtx)
print('2nd\n',mtx2)
print('merge\n',mtx3)
..

result
```1st
(0, 0) 1
(0, 2) 1
(1, 2) 1
(2, 0) 1
(2, 1) 1
(2, 2) 1
2nd
(0, 0) 1
(0, 1) 1
(1, 2) 1
(2, 0) 1
(2, 1) 1
(2, 2) 1
merge
(0, 0) 2.0
(0, 1) 1.0
(0, 2) 1.0
(1, 2) 2.0
(2, 0) 2.0
(2, 1) 2.0
(2, 2) 2.0```

### How to convert a scipy csr_matrix back into lists of row, col and data?

refer to code

..
Define matrix & check values
from scipy.sparse import csr_matrix
import numpy as np
row = np.array([0, 0, 1, 2, 2, 2])
col = np.array([0, 1, 2, 0, 1, 2])
data = np.array([1, 1, 1, 1, 1, 1])
mtx2 = csr_matrix((data, (row, col)), shape=(3, 3))
print(mtx2) #matrix print out
print(mtx2.toarray()) #print out by array

>
```(0, 0) 1
(0, 1) 1
(1, 2) 1
(2, 0) 1
(2, 1) 1
(2, 2) 1```
`>`
```[[1 1 0]
[0 0 1]
[1 1 1]]```
..

...
get back the row, col and data value from matrix
c = mtx2.tocoo()
print(c.row)
print(c.col)
print(c.data)

>
```[0 0 1 2 2 2]
[0 1 2 0 1 2]
[1 1 1 1 1 1]```
...