24. Formatting text strings¶

A formatted text string literal is a text string that begins with the letter 'F ' or 'f' and containing replacement fields delimited by braces { }. Replacement fields contain Python variables and, optionally, the formatting to give to the variable's contents.

If you want to print a key, you need to duplicate it: {{ or }}.

Example:

>>> nombre = 'Guido'
>>> apellido = 'van Rossum'
>>> f'El creador de Python es {nombre} {apellido}'
    'El creador de Python es Guido van Rossum'

>>> numero = 7
>>> f'James Bond es el agente {numero:03d}'
    'James Bond es el agente 007'

Exercises¶

Repeat the following exercise with your own name.

Exercise:

>>> nombre = 'Anselmo'
>>> f'{nombre:>20}'    # Justificado a la derecha
    '             Anselmo'
>>> f'{nombre:<20}'    # Justificado a la izquierda
    'Anselmo             '
>>> f'{nombre:^20}'    # Centrado
    '      Anselmo       '
>>> f'{nombre:_^20}'   # Centrado con relleno '_'
    '______Anselmo_______'

Repeat the following exercise with the number variable number = 72. On the last line change the number to your year of birth.

Exercise:

>>> nmr = 44
>>> f'{nmr:10d}'    # Formato decimal entero. Longitud 10
    '        44'
>>> f'{nmr:+10d}'   # Formato decimal entero con signo. Longitud 10
    '       +44'
>>> f'{nmr:10X}'    # Formato hexadecimal en mayúsculas. Longitud 10
    '        2C'
>>> f'{nmr:010b}'   # Formato binario con ceros a la izquierda. Longitud 10
    '0000101100'
>>> f'{nmr:c}'      # Formato de número a Unicode
    ','
>>> f'{128512:c}'   # Formato de número a Unicode
    '😀'
>>> f'{2023:c}'     # Formato de número a Unicode
    'ߧ'

Repeat the following exercise with the variable e = 2.71828. Remember that in Python decimals are always separated with a period, not a comma.

Exercise:

>>> pi = 3.14159
>>> # Número de punto flotante con 10 espacios en total y 3 decimales
>>> f'{pi:10.3f}'
    '     3.142'
>>> f'{pi:010.3f}' # Igual que el primero, con ceros a la izquierda
    '000003.142'
>>> f'{pi:10.0f}'  # Igual que el primero, con cero decimales
    '         3'
>>> f'{pi:10.4e}'  # Igual que el primero, en notación científica
    ' 3.142e+00'

Write a program that prompts for a character from the keyboard and returns the next 10 Unicode characters.

Use the ord() function to convert the character to its Unicode number.

Clue:

caracter = input('Introduce un caracter: ')
numero = ord(caracter[0:1])
for code in range(numero+1, numero+11):
    print(f'Código: ...  caracter: ... ')

Exit:

Introduce un caracter: ç
Código: 0x000E8 caracter: è
Código: 0x000E9 caracter: é
Código: 0x000EA caracter: ê
Código: 0x000EB caracter: ë
Código: 0x000EC caracter: ì
Código: 0x000ED caracter: í
Código: 0x000EE caracter: î
Código: 0x000EF caracter: ï
Código: 0x000F0 caracter: ð
Código: 0x000F1 caracter: ñ

Try entering different characters from the keyboard. Try copying from the Internet and pasting symbols, emojis, Greek and Cyrillic letters, etc.

Write a function that returns the value of an RGB color in Hexadecimal. The three parameters of the function will be three decimal numbers R, G and B (Red, Green and Blue) that must be in the range from 0 to 255. If any number is greater than 255 or less than 0, it must be trimmed to the allowed value .

Hint: Define a function that limits the value of each number and formats it to hexadecimal format. Then you can define a second function that calls the first function three times with the values of the three colors.

Remember that hexadecimal values must be in capital letters and must have two digits. The way to convert a variable to two-digit hexadecimal is to add the following format to the variable: f'{variable:02X}'.

Example:
```
rgb(128, 196, 4)
rgb(500, -5, 64)
```
Exit:
```
80C404
FF0040
```