Documentation officielle de Python

2.4.4 Integer and long integer literals

Integer and long integer literals are described by the following lexical definitions:

longinteger	::=	integer ("l" \| "L")
integer	::=	decimalinteger \| octinteger \| hexinteger
decimalinteger	::=	nonzerodigit digit* \| "0"
octinteger	::=	"0" octdigit+
hexinteger	::=	"0" ("x" \| "X") hexdigit+
nonzerodigit	::=	"1"..."9"
octdigit	::=	"0"..."7"
hexdigit	::=	digit \| "a"..."f" \| "A"..."F"

Although both lower case "l" and upper case "L" are allowed as suffix for long integers, it is strongly recommended to always use "L", since the letter "l" looks too much like the digit "1".

Plain integer literals that are above the largest representable plain integer (e.g., 2147483647 when using 32-bit arithmetic) are accepted as if they were long integers instead.^2.1 There is no limit for long integer literals apart from what can be stored in available memory.

Some examples of plain integer literals (first row) and long integer literals (second and third rows):

7     2147483647                        0177
3L    79228162514264337593543950336L    0377L   0x100000000L
      79228162514264337593543950336             0xdeadbeef

Footnotes

... instead.^2.1: In versions of Python prior to 2.4, octal and hexadecimal literals in the range just above the largest representable plain integer but below the largest unsigned 32-bit number (on a machine using 32-bit arithmetic), 4294967296, were taken as the negative plain integer obtained by subtracting 4294967296 from their unsigned value.

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