Assignment syntax in Python

There are 6 types of replication syntax in Python

Basic Form

' spam '

Tuple Assignment

' spam ' ' Ham '

List Assignmen

>>>[spam, ham] = ['spam'ham']

Sequence Assignment

' spam '

Extended sequence Unpacking (Python 3.X)

>>>a, *b ='spam'>>>a's'>>>b#b The result of the assignment is a list['P','a','m']>>>a, *b, C ='spam'>>>a's'>>>b['P','a']>>>C'm'

There are five points to note about this type of replication:

1 for an assignment result with an * number variable, always a list, even if only one element is included

2 If no remaining value is assigned to a variable with an * number, it is an empty list

 >>>>a, B, C, *e, d =  " spam  Span style= "COLOR: #800000" > " >>>a   " s   " >>>b   " p   " >>>c   " a   " >>>d   " m   " >>>e #   Independent of the position of the * variable  [] 

3 error if 2 or more than 2 * variables appear in an assignment statement

4 The number of variables and the number of values do not match, will also error

' spam '    # The number of values is too low  Not enough values to unpack (expected 5, got 4)'spam'    #
     variable number is too small valueerror:too many values to unpack (expected 2)

5 with * Number variable is not in a sequence, will also error

>>>*a ='spam'syntaxerror:starred Assignment target must beinchA listortuple>>>*a, ='spam'       #that's OK .>>>a['s','P','a','m']

Augmented assignment

>>>spams = 42>>>spams + = 42>>>spams84

Augmented assignment has 3 advantages:

1 simple, can be less typing, haha

2 in the form of x + = y, if x is a complex object, then augmented assignment only runs the code once for X, and if it is written as x = x + y, the code for x runs two times

3 in some cases, x+=y is an optimization

>>>l = [1, 2]>>>l = L + [3, 4]      #  This form of + will create a temporary, new list, and then copy the L and the array to be concatenated, Finally, this temporary, new list is assigned to L, inefficient >>>l[1, 2, 3, 4]>>>l = [1, 2]>>>l + = [3, 4]    #  This form directly changes L, does not create new objects, nor copies, high efficiency >>>l[1, 2, 3, 4]

Assignment syntax in Python