[Introduction to Udemy Python3 + Application] 11. Character strings

** * This article is from Udemy "[Introduction to Python3 taught by active Silicon Valley engineers + application + American Silicon Valley style code style](https://www.udemy.com/course/python-beginner/" Introduction to Python3 taught by active Silicon Valley engineers + application + American Silicon Valley style code style ")" It is a class notebook for myself after taking the course of. It is open to the public with permission from the instructor Jun Sakai. ** **

■ Basic character string

print_standard

print('hello')
print("hello")

result

hello
hello

If you specify a string in print (), you can use either '' or " ".

■ When there is a "'" in the character string

◆ Enclose with " "

print_'

print("I don't know.")

result

I don't know.

If you enclose it in " ", it will be output properly.

◆ An error will occur if enclosed in ''

print_'

print('I don't know.')

result

    print('I don't know.')
                 ^
SyntaxError: invalid syntax

If you enclose it with '', the "'" in the character string will be judged as the end of the enclosing, resulting in an error.

◆ Use \ to avoid errors

print_'

print('I don\'t know.')

result

I don't know.

By putting \ before ' in the character string, you can avoid the judgment as a group.

print_'

print('say "I don\'t know."')
print("say \"I don't know.\"")

result

say "I don't know."
say "I don't know."

application.

■ When there is "\ n" in the character string

◆ Line break \ n

print_\n

print('Hello. \nHow are you?')

result

Hello.
How are you?

I've dealt with the fact that \ n becomes a" newline "before.

◆ Incorrectly judged as \ n

print_\n

print('C:\name\name')

result

C:
ame
ame

I wanted to display "C: \ name \ name", but the \ n part was judged as a line break.

◆ Avoid judgment using r

print_\n

print(r'C:\name\name')

result

C:\name\name

In that case, you can print the character string as it is by adding r, which is the acronym of" raw ", to the beginning of the character string.

■ Line breaks

new_line

print("""
line1
line2
line3
""")

result

line1
line2
line3

By using " "" "" " as above, you can write easy-to-read code without using \ n` to write in one line.

new_line

print('#######')
print("""
line1
line2
line3
""")
print('#######')

result

#######

line1
line2
line3

#######

However, with this writing method, blank lines will be inserted above and below the character string.

new_line

print('#######')
print("""\
line1
line2
line3\
""")
print('#######')

result

#######
line1
line2
line3
#######

By putting \ in this way, it means "start the next code on the next line".

■ Use operators

◆ Strings and operators

operator

print('Hi.' * 3 + 'Mike.')
print('Py' + 'thon')
print('Py''thon')

result

Hi.Hi.Hi.Mike.
Python
Python

You can also combine operators with strings. If you simply connect the strings, they will be connected and printed without writing +.

◆ Parallel of variables and strings

operator

prefix = ('Py')

print(prefix'thon')

result

    print(prefix'thon')
                     ^
SyntaxError: invalid syntax

However, when a character string is assigned to a variable, + cannot be omitted.

operator

prefix = ('Py')

print(prefix + 'thon')

result

Python

I was able to connect properly with +.

◆ If you prefer to omit +

operator

print('aaaaaaaaaaaaaaaaaaaaaaaaaaa'
      'bbbbbbbbbbbbbbbbbbbbbbbbbbb')

result

aaaaaaaaaaaaaaaaaaaaaaaaaaabbbbbbbbbbbbbbbbbbbbbbbbbbb

If you want to connect long strings and display them, writing them like this makes the code easier to read. (If you write in one line, it may not fit in the screen size and it is difficult to see.)