Study from Python Hour4: Object-oriented ②

When I tried to do something with Python, I first searched for a sample script and somehow executed it.
7 hours I want to hit REST API with automatic execution, check the result, and even operate the VM
This time it's an object-oriented continuation. However, the method confirmation level

Learning materials

Learn the basics in just one day! A super introduction to Python
https://a.r10.to/hbHMiv

Past posts

environment

Windows
Python Ver3 series

Immutable object

Last time, I manipulated the list object. As a method I was able to modify the instance itself (such as adding a value to the end of the list)
Apart from such things, there is something that "the data that the instance has never changes", and the representative is the character string type.

Manipulating immutable objects

String methods do not change their instance.
Example where the object does not change when using the method

>>> my_str = 'hello Python!!'
>>> my_str2 = my_str.upper()
>>>
>>> ###Show original value
>>> print('Original: ', my_str)
Original:  hello Python!!             ###You can see that it has not changed
>>>
>>>
>>> ###Display the value after string operation
>>> print('Return my_str2: ', my_str2)
Return my_str2:  HELLO PYTHON!!

It was confirmed that the instance (my_str) that called the method did not change after calling the method.
The same is true for the replace method, which replaces a string.

>>> my_str = 'hello Python!!'
>>> my_str2 = my_str.replace('hello', 'kill')
>>>
>>>  ###Show original value
>>> print('Original: ', my_str)  
Original:  hello Python!!                 ###You can see that it has not changed
>>>
>>>
>>> ###Display the value after string operation
>>> print('Return my_str2: ', my_str2)
Return my_str2:  kill Python!!

The replace method seems to change the instance, but it's not confusing if you remember that "a string type method does not change the original instance".

Let's play with the method of the string type instance

String manipulation is often used in Python programming, so try various things.

>>> ###format method. The one who is taken care of by string concatenation
>>> in_name = 'Pochi'              ###Specify name and age with variables
>>> in_age  = 3
>>>
>>>### {}Insert the value of the variable inside. This is a fashionable method
>>> my_text = 'My name is {}. {} years old.'.format(in_name, in_age)
>>> print(my_text)
My name is Pochi. 3 years old.
>>>

>>> ###startswith method. Check if there is a beginning of the character string. bool type and True/False will be returned.
>>> print('AHV-log:aaa'.startswith('AHV'))　　　　　###It seems easy to use if there is a log file name at the beginning of the log
True
>>> print('mail-log:aaa'.startswith('AHV'))
False

>>> ###Same usage for endswith method


>>> ###strip method. Remove whitespace before and after the string
>>> print('  aaa    ') 
  aaa
>>> print('  aaa    '.strip())
aaa　　　　　###The leading and trailing spaces have been removed. Useful when dealing with stupid log files
>>>

>>> ###split method. When retrieving data separated by commas. Can be used with JSON
>>> my_text ='aaa,bbb,ccc'
>>> my_list = my_text.split(',')    ###Split with commas
>>>
>>> print(my_list)
['aaa', 'bbb', 'ccc']
>>>

>>> ###Join with join method (note that you are doing it with a text object method, not a list)
>>> my_list = ['aaa', 'bbb', 'ccc']
>>> print(','.join(my_list))
aaa,bbb,ccc         ###I was able to separate the list with commas
>>>

>>> ###String comparison in operator (whether string A is contained in string B). It seems to be used in a conditional expression
>>> print('aaa' in 'aaaaaaa')
True
>>> print('aaa' in 'baaaaaa')
True
>>> print('aaa' in 'aaabbbaaa')
True
>>> print('aaa' in 'ccc')
False
>>>

Somehow I understand how to use it

Method chain

It is also possible to operate with a method on an instance of the return value of the method (it is faster to see the example)

>>> my_name = 'pochi'
>>> my_intro = 'My name is {}.'.format(mnname)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'mnname' is not defined
>>> my_intro = 'My name is {}.'.format(my_name)
>>> my_intro.upper()
'MY NAME IS POCHI.'      ###This much processing
>>>


>>> my_name = 'pochi'
>>> print('My name is {}.'.format(my_name).upper())
'MY NAME IS POCHI.'　　　　###Can be done in one line
>>>

Can be omitted as above, but moderately. Readability is reduced.

This summary

Strings are mutable objects so let's understand and use them
It takes an hour to check this amount. It's almost 7 hours passed w

For Quotations / Lightning Talk

Functions and methods are used to improve readability, but overuse will reduce readability and maintainability.