Reason for publication

・ Because Qiita's comment mentioned the intensional expression, and I thought it was an opportunity to understand it now. (I've heard the comprehension itself in the "Python Tutorial", but it seemed difficult and I ran away. Now is my chance!)

Comprehension grammar

The grammar itself doesn't seem to be as difficult as it looks. (I ran away because I thought it would be difficult ... sweat)

[Processing content for x in list etc.]

Personally, when I disassembled it as follows, I personally felt comfortable.

After "for", the form is the same as a normal Python for statement. Impression that the processing content is like a for statement that came before.

Sample code (included notation)

Code that triples each element

`naiho.py`


num_list = [-4, -3, -2, -1, 0, 1, 2, 3, 4]

naiho = [x * 3 for x in num_list]
print(naiho)

Or a code to put the last name in the name

`kawaii.py`


gotobun = ["ithika", "nino", "miku", "yotsuba", "itsuki"]

hanayome = ["nakano " + z for z in gotobun]
print(hanayome)

Output result (included notation)

Calculation can be done normally

[-12, -9, -6, -3, 0, 3, 6, 9, 12]

It's easy to create a string. It seems that there are many situations that can be used if devised.

['nakano ithika', 'nakano nino', 'nakano miku', 'nakano yotsuba', 'nakano itsuki']

Sample code (no inclusion notation ver)

If you try to process the above two sample codes with a for statement, it will look like the following.

`no_naiho.py`


num_list = [-4, -3, -2, -1, 0, 1, 2, 3, 4]
not_naiho = []

for y in num_list:
  y *= 3
  not_naiho.append(y)

print(not_naiho)

`no_kawaii.py`


gotobun = ["ithika", "nino", "miku", "yotsuba", "itsuki"]
hanayome = []

for a in gotobun:
  a = "nakano " + a
  hanayome.append(a)

print(hanayome)

Output result (no inclusion notation ver)

It doesn't change depending on whether it is included or not, but I will write it for the time being.

[-12, -9, -6, -3, 0, 3, 6, 9, 12]

['nakano ithika', 'nakano nino', 'nakano miku', 'nakano yotsuba', 'nakano itsuki']

Impressions

・ I felt that by using the comprehension notation, I could write the for statement more simply than I expected. ・ If you are not familiar with the comprehension notation, write the for and below first, and then write the processing content at the end. I thought I would be less confused.

[Python] Let's write briefly about comprehensions