Python: Literals

Numerical literals

A numerical value can be expressed in its hexadecimal representation by prefixing it with 0x

>>> 0xdeadbeef
3735928559

Similarly, a numerical value can also be expressed as in octal representation by prefixing it with 0o (the first character is a zero, the second one an upper or lowercase o).

>>> 0o777
511

Same idea, but as byte representation (0b…, compare with b'…' below). The following expression calculates 4*3:h

0b100 * 0b0011

In numerical literals, underscores can be used to make them more readable by a human eye. Such underscores are simply skipped by the parser.

>>> print(21_000_000_000 / 7_000_000)
3000.0

A number that is suffixed with a j becomes a complex number:

>>> type(4.2j)
<class 'complex'>

String literals

Strings are either single- or double-quoted.

Strings in double quotes. Note how two strings are automatically concatenated:

>>> print("foo\nbar\\baz" " x\"y")
foo
bar\baz x"y

Strings in single quotes:

>>> print('foo\nbar\\baz' ' x\'y')
foo
bar\baz x'y

R-Strings

With R-strings, a backslash has no special meaning and represents itself. The R of the R-String stands for raw.

>>> print(r"foo\bar")
foo\bar

An R-string cannot have a trailing slash!

>>> print(r"foo\bar\")
…
SyntaxError: EOL while scanning string literal

A trailing slash can be added by the automatic string concatenation:

>>> print(r"foo\bar" "\\")
foo\bar\

F-Strings

An f-string replaces expressions within curly braces with they values the evaluate to. The f in f-strings stands for formatted string (see also the format method of the string object).

>>> a=7
>>> b=6
>>> print(f'{a} * {b} = {a*b}')
7 * 6 = 42

In f-strings, a number can be printed with a comma as thousand separator like so:

>>> cost_per_item = 19_999
>>> items = 61
>>> print(f'Total cost: {cost_per_item * items:,}')
Total cost: 1,219,939

A variable followed by an equal sign (=) expands to both, the variable name and its value:

>>> var = 42
>>> print(f'{var=}')
var=42

In an f-string, a curly brace must be escaped by itself:

print(f'{{ within ONE pair of curly braces }}')

Multi-line strings

«Normal» strings cannot have new lines in them:

>>> print('first line
          ^
SyntaxError: unterminated string literal (detected at line 1)

In order to create multi line strings, the string must be embedded in «triple quotes» (single or double):

>>> txt = """foo
... bar\n
... baz"""
>>>
>>> print(txt)
foo
bar

baz

Bytes object

b'…' creates a bytes object:

>>> name = b'Ren\xc3\xa9'
>>> type(name)
<class 'bytes'>
>>> print(name.decode('utf-8'))
René

Identity of literals

Even literals have an identity:

>>> id(42)
140707326270400