Python in a Nutshell, 2nd Edition

Expressions and Operators

An expression is a phrase of code that Python evaluates to produce a value. The simplest expressions are literals and identifiers. You build other expressions by joining subexpressions with the operators and/or delimiters in Table 4-2. This table lists operators in decreasing order of precedence, higher precedence before lower. Operators listed together have the same precedence. The third column lists the associativity of the operator: L (left-to-right), R (right-to-left), or NA (nonassociative).

Table 4-2. Operator precedence in expressions

Operator	Description	Associativity
`expr,...`	String conversion	NA
{key:expr,...}	Dictionary creation	NA
[expr,...]	List creation	NA
(expr,...)	Tuple creation or just parentheses	NA
f(expr,...)	Function call	L
x[index:index]	Slicing	L
x[index]	Indexing	L
x.attr	Attribute reference	L
x**y	Exponentiation (x to yth power)	R
~x	Bitwise NOT	NA
+x, -x	Unary plus and minus	NA
x*y, x/y, x//y, x%y	Multiplication, division, truncating division, remainder	L
x+y, x-y	Addition, subtraction	L
x<<y, x>>y	Left-shift, right-shift	L
x&y	Bitwise AND	L
x^y	Bitwise XOR	L
x|y	Bitwise OR	L
x<y, x<=y, x>y, x>=y, x<>y, x!=y, x==y	Comparisons (less than, less than or equal, greater than, greater than or equal, inequality, equality)[a]	NA
x is y, x is not y	Identity tests	NA
x in y, x not in y	Membership tests	NA
not x	Boolean NOT	NA
x and y	Boolean AND	L
x or y	Boolean OR	L
lambda arg,...: expr	Anonymous simple function	NA
[a] <> and != are alternate forms of the same operator. != is the preferred version; <> is obsolete. ...