python personal notes


I hardly remember Python! However, I need to use it often, and I feel that I am investigating the same thing many times, so I will leave a memorandum in the future. I will add it every time I check it.

It may not be useful because it is a personal memo, but please use it if you like.

Type conversion

test_str = '100'

No line breaks with print ()

print('text', end='')

PATH generation

# add path
path = './'
path = os.path.join(path, 'dir')
# generate path
path = ['./', 'dir']
path = os.path.join(*path_list)

Loop with index number

If you use ʻenumerate ()`, you can get it at the time of loop without writing the addition of the counter.


test_list = ['test1', 'test2', 'test3']
for idx, test in enumerate(test_list):
  print('{} : {}'.format(idx, test))

String manipulation

Splitting strings


test_str = 'Hello World'
test_str.split() #Separate by space →['Hello', 'World']
test_str.split('o') #'o'Separated by →['Hell', ' W', 'rld']

String concatenation


test_str = 'Hello World'
test_list = test_str.split()
test_join = ''
test_join = test_join.join(test_list) #Between`test`Put and combine →'HelloWorld'
test_join = ' '
test_join = test_join.join(test_list) #Between`test`Put and combine →'Hello World'

String replacement


test_str = 'Hello World'
test_str.replace('o', 'p') #'o'To'p'Convert to →'Hellp Wprld'
test_str.replace('o', 'p', 1) #only 1 time'o'To'p'Convert to →'Hellp World'


Delete key

If you just want to delete it, you only need the second line, but considering that the key does not exist, it seems safer to keep it in the second line.

if 'key' in dic:
  del dic['key']

If you try to delete the key inside the loop, you will get an error, so do the following:

for key in list(dic):
  if ...: #Favorite conditions
    del dic[key]



import math
from math import * ## math.No need to put on


math.pow(x, y)





import numpy as np

Matrix generation

#Zero matrix generation
zeros_array = np.zeros((row, column))
#Ichi matrix generation
ones_array = np.ones((row, column))
#Numeric matrix generation
value_array = np.full((row, column), value)

inner product, B)



import cv2

Load image

img = cv2.imread(path)

Draw image

cv2.imshow('img', img)
cv2.waitKey(0) #The argument is the drawing time

Write image

cv2.imread(path, img)


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