List operations in Python python

Python's list operation is powerful and convenient (relative to Java)
Simple, regular operation is not said (this is not an introductory tutorial), introduce a few very characteristic examples

Add to

# Append to End (append) Li = [1, 2, 3, 4, 5]li.append (6) print (' li =%s '% li) # output: Li = [1, 2, 3, 4, 5, 6]# append a list (extend) Li2 = [' A ' , ' B ', ' C ', ' d ', ' E ']li.extend (li2) print (' li =%s '% li) # output: Li = [1, 2, 3, 4, 5, 6, ' A ', ' B ', ' C ', ' d ', ' e ']# list and list can also do addition  Li_plus = li + li2print (' li_plus =%s '% li_plus) # output: Li_plus = [1, 2, 3, 4, 5, 6, ' A ', ' B ', ' C ', ' d ', ' e ', ' A ', ' B ', ' C ', ' d ', ' e ']

Delete

# remove elements from list li = [1, 2, 3, 4, 5]li.remove (3) print (' li =%s '% li) # output: Li = [1, 2, 4, 5]
# Delete element according to Index del li[3]print (' li =%s '% li) # output: Li = [1, 2, 4]

Intercept (also called slice operation)
Format: [Start:end:step]. Remember this format and you can play with your imagination.

Li = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
# every two elements take a li2 = Li[::2]print (' li2 =%s '% li2) # output: Li2 = [0, 2, 4, 6, 8, 10]# the last element of elements = Li[-1]print (' element =%s ') % Element) # output: element = 10# copy (after copy is a new object) Li2 = List (li) print (' Li2 =%s '% li2) # output: Li2 = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 1 0]

Extract and delete (pop)

Li = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]# extracts and removes the last element Li.pop ()    # equals Li.pop ( -1) print (' li =%s '% li) # output: Li = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]# extracts and deletes the first element (or nth Element) Li.pop (0) print (' li =%s '% li) # output: Li = [1, 2, 3, 4, 5, 6, 7, 8, 9]

Sort

# positive Order Li = [3, 1, 5, 8, 0, 9, 2, 6, 7, 4]li.sort () print (' li =%s '% li) # output: Li = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]# reverse li = [3] , 1, 5, 8, 0, 9, 2, 6, 7, 4]li.sort (reverse=true) print (' li =%s '% li) # output: Li = [9, 8, 7, 6, 5, 4, 3, 2, 1, 0]# flip (not in reverse order) Li = [3, 1, 5, 8, 0, 9, 2, 6, 7, 4]li.reverse () print (' li =%s '% li) # output: Li = [4, 7, 6, 2, 9, 0, 8, 5, 1, 3]

List parsing
How to create a new list efficiently, based on an existing list
Format: [expression for iter_val in iterable]

# each item in the list takes square li = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]li2 = [i**2 for i in Li]print (' li2 =%s '% li2) # output: Li2 = [0, 1, 4, 9, 16, 25, 36, 49, 64, 81]# only a number greater than 5 takes the square.  An expression can also be an if statement li = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]li2 = [i**2 If i > 5 else I for I in li]print (' li2 =%s '% li2) # output: Li2 = [0, 1, 2, 3, 4, 5, 36, 49, 64, 81]

Format: [expr for Iter_var in iterable if COND_EXPR]

# only take elements that are not None li = [0, 1, 2, 3, 4, 5, None, 6, 7, 8, 9]li2 = [i-I in Li if I am not none]print (' li2 =%s '% li2) # output: Li2 = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

Format: [expr for Iter_var in iterable for Var in iter_var]

# Expand a two-dimensional list of li = [[0, 1, 2], [3, 4, 5, 6], [7, 8, 9]]li2 = [j for I in Li-J in i]print (' li2 =%s '% li2) # output: Li2 = [0, 1 , 2, 3, 4, 5, 6, 7, 8, 9]

Elements in a connection list (join)

Li = [' aaa ', ' BBB ', ' CCC ', ' ddd ']li2 = ', '. Join ' print (' li2 =%s '% li2) # output: Li2 = AAA, BBB, CCC, DDD

List operations in Python python