python tips summary

I will leave it as a memorandum.

Character → ascii. conversion from ascii to characters

Get ASCII code with ʻord`

>>> ord('a')
97

Get characters with chr

>>> chr(97)
a

List generation

If you write in a comprehensive list, the execution speed is fast because it is not saved in memory.

num = 1000000000

#Normal writing
list_1 = []
for i in range(num):
   list_1.append(i)

#List comprehension
list_2  = [i for i in range(num)]

In addition, @konandoiruasa advised that the following items are based on the inclusion notation and are slightly faster.

import numpy as np
a = list(np.arange(num, dtype=int))

"Join" to join various things

You can join strings, numbers, and paths with join. Use with " ". join.

list = ['a', 'b', 'c']
result = ''.join(list)
print(result)

## abc

If list has letters and numbers, convert them all to str with map function

list = ['a', 'b', 1 ]
result = map(str, list)
result1 = ''.join(result)
print(result1)

## ab1

Split with split

str1 = "a,b,c"
sep = str1.split(",")
print(sep)
## ['a', 'b', 'c’]

Conversion of np.array and list


import numpy as np
list = [1,2,3]

a = np.array(list)
print(a)
## array([1, 2, 3])

b = a.tolist()
print(b)
##[1, 2, 3]

How to export to csv


import pandas as pd

log = pd.DataFrame(
         columns=['epoch', 'lr', 'train_loss', 'val_loss']
         )

tmp = pd.Series([ epoch, lr, train_loss, val_loss ], index=log.columns) 
  
log = log.append(tmp, ignore_index=True) 
log.to_csv('log.csv'), index=False)

At the end

I would like to add more from time to time. If you have any suggestions, please do not hesitate to contact us.