Things to keep in mind when using Python for those who use MATLAB

Things to keep in mind when using Python for those who use MATLAB

There was a site that wrote notes on MATLAB and Python that I use at work, so I will keep it as a memorandum.

・ 11 points to note when starting Python for those who are accustomed to MATLAB

https://datachemeng.com/matlab_to_python/

What I was addicted to when I started using Python

1. Assignment by "=" is not a copy of the value, but a reference. Unintended data changes may occur

Countermeasure: If you want to copy the value, use .copy ().

import numpy as np
# =============================================================================
# b += 5 ->The original a also changes.
# =============================================================================
a = np.array([1,2,3])
print('a = ')
print(a)
print('\n')

b = a

b += 5  #The original a also changes.
print('b = a , b +=After running 5')
print('a = ')
print(a)
print('b = ')
print(b)
print('\n')

# =============================================================================
# 'b = a , b = b + 5 ->The original a does not change.
# =============================================================================
a = np.array([1,2,3])
b = a

b = b + 5 #The original a does not change.
print('b = a ,b = b +Run 5')
print('a = ')
print(a)
print('b = ')
print(b)
print('\n')

# =============================================================================
# 'b = a , b[0] = 100 ->The original a also changes.
# =============================================================================
a = np.array([1,2,3])
b = a

b[0] = 100
print('b = a ,b[0] =After running 100')
print('a = ')
print(a)
print('b = ')
print(b)
print('\n')

# =============================================================================
# b = a.copy() b[0] = 100 ->The original a also changes.
# =============================================================================
a = np.array([1,2,3])
b = a.copy()

b[0] = 100
print('b = a.copy(),b[0] =After running 100')
print('a = ')
print(a)
print('b = ')
print(b)
print('\n')

a = 
[1 2 3]


b = a , b +=After running 5
a = 
[6 7 8]
b = 
[6 7 8]


b = a ,b = b +Run 5
a = 
[1 2 3]
b = 
[6 7 8]


b = a ,b[0] =After running 100
a = 
[100   2   3]
b = 
[100   2   3]


b = a.copy(),b[0] =After running 100
a = 
[1 2 3]
b = 
[100   2   3]

2. Array type conversion is not performed automatically. (Only when performing operations on array elements)

Countermeasure: When creating an array, do not set it with an integer, but specify it with a decimal number. Or specify the type with dtype = float.

In any case, attention to the type is essential.