day4 - manipulation of python lists and tuples
1. List: Store a large number of ordered data of various data types, retaining the format of the original data
CRUD
Add: three methods
append (variable expression) method
list.append(variable expression) appends to the end of the list
insert(index, variable expression) method, insert by index
list.insert(index, variable expression)
extend("variable expression")
list.extend("variable expression"), split the variable into next-level elements, iteratively append to the end of the list
Deletion: Four Methods
pop(index) delete by index
remove(element) remove by element
clear(list) clear
del, delete by index, delete by slice, delete from memory
del list[index], del list[index 1, index 2], del list
Change: two methods, change by index, change by slice
list[index] = new variable
list[index1,index2] = new variable, delete elements between indexes (regardless of head and tail), split the variable into next-level elements, and iteratively fill in the index space,
Lookup: index, slice, for loop
Other methods
len(list) method, list.count(variable) method, sort sort() method, forward sort, reverse sort sort(reverse=True), reverse order reverse() method
index() method, list has no find method
Nesting of for loops, iterating over each element of each level in the output list (from left to right)
type() method, query element data type, and can be used for conditional judgment
The range() method is equivalent to generating a list of numbers with a set range. The starting number is 0 by default. It can be omitted. The positive and negative steps can be added to traverse the array.
Nesting of lists: multi-level index queries, traversing lists with multi-level for loops
Tuple: It is called an immutable list, there is no addition, deletion and modification function, only query function, through index, slice query, and general methods len(), count()
Although the next level of the tuple, the elements of the tuple cannot be modified, but the next level of the tuple and the non-element elements of the lower level can be modified, and the modification method is the same as that of the list.
2. Review of yesterday's content
Integer method bit_length() method, calculation
How to work with strings
center(width,"fill character"), str is centered, filling characters on both sides
strip ("string") removes the leading and trailing spaces, tab keys, newlines by default, and can also remove the specified characters at the beginning and the end. If the specified character contains multiple elements, all the elements of the specified character at the beginning and the end are removed.
lstrip() to the head, rstrip() to the tail,
"Character".join(list), convert the list to a string, connect with empty elements by default
list.split("split character", count), split the string into lists from left to right, the number can be set
upper(), lower() method, all uppercase, all lowercase
The capitalize() method changes the first element of the string to uppercase (if the first element is not an English letter, there is no change), and the rest of the English letter elements are lowercase
title() method, capitalize the first letter of English words separated by non-English characters, and lowercase the rest of the letters
swapcase() method, swap the upper and lower case of English letters
find(), index() methods, return the first index of the first specified character, return -1 if the find is not found, and report an error if the index is not found
startswith(), endswith() method, can be sliced, query whether the specified string starts and ends
Generic methods, len(), count()
format formatted output three methods
str = "{}{}{}".format (the first {} padding character, the second {} padding character, the third {} padding character), ordered
Format method by index, str=”{2}{0}{2}”.format (string at index 0, string at index 1, string at index 2), ordered
Format method by keyword, str = "{keyword1}{keyword3}{keyword2}".format(keyword3:"str1",keyword1:"str2",keyword3:" str3")
How to determine the composition of string elements
.isalbum() numbers and letters
.isdigit() digit composition
.isalpha() letter composition
The type()== method can also be used as a judgment condition for if