13_python data type String strengthening the path of _python programming

We've talked about Python data types before, but not in depth, and we've learned more about the use of Python data types in this section.

There are many ways to list data types, and we're here to introduce you

1.append

The Append method is used to append an object to the end of the list.

For example, the following code

In [1]: My_list = [1, 2, 3, 4]in [2]: My_list.append (5) in [3]: my_listout[3]: [1, 2, 3, 4, 5]

Note Append, like other methods, modifies only the list and does not return a value

2.clear

Method clear clears the contents of the list in place

For example, the following code

In [4]: My_list = [1, 2, 3, 4]in [5]: My_list.clear () in [6]: My_listout[6]: []

This function can also be achieved by slicing

In [7]: My_list = [1, 2, 3, 4]in [8]: my_list[:] = []in [9]: my_listout[9]: []

3.copy

Copy is used to replicate the list, but be aware that he simply associates a variable to this list

The following is simply an assignment for a simple copy

In [ten]: My_list = [1, 2, 3, 4]in [all]: Other_list = my_listin []: other_listout[12]: [1, 2, 3, 4]

For My_list and Other_list to point to a different list, you must use copy

For example, the following code

in [[]: My_list = [1, 2, 3, 4]in [+]: Other_list = my_list.copy () in []: other_listout[17]: [1, 2, 3, 4]in []: Other_ List[0] = ' one ' in [[]: other_listout[19]: [' One ', 2, 3, 4]in []: my_listout[20]: [1, 2, 3, 4]

You can see that the two list is pointing to a memory address that is not the same

4.count

Calculates how many times the specified element appears in the list

in [+]: word_list = [' to ', ' is ', ' or ', ' not ', ' to ', ' being ']in [$]: Word_list.count (' to ') out[22]: 2

Note that for multidimensional lists, things can be a little different

In [all]: Multi_list = [1, [1, 2], 1, [1, 2, 3]]in []: Multi_list.count (1) out[24]: 2In []: Multi_list.count ([up]) out[2 5]: 1

5.extend

You can attach multiple values to the end of the list, which means you can connect two lists, or you can use a list to extend another list

in [+]: a_list = [1, 2]in [+]: b_list = [3, 4]in []: A_list.extend (B_list) in []: a_listout[29]: [1, 2, 3, 4]

This looks a bit like the following lines of code, connecting two of lists

in [+]: a_list = [1, 2]in []: B_list = [3, 4]in [+]: A_list + b_listout[32]: [1, 2, 3, 4]

But it's important to note that the result is not directly assigned to the value

In addition to using the Extend method above, we can also use the slice operation

In [all]: A_list = [1, 2]in []: B_list = [3, 4]in [in]: A_list[len (a_list):] = B_listin []: a_listout[42]: [1, 2, 3, 4]

But I have to say, the readability is poor.

6.index

Method index finds the first occurrence of the specified value in the list

For example, the following code

in [+]: my_list = [1, 2, ' susmote ', ' ayesup ', ' ayesup ', ' Susmote ', 2, 1]in []: My_list.index (' Susmote ') out[44]: 2

To emphasize here, index just looks for the first occurrence of the index

7.insert

The Insert method inserts an object into the list

For example, the following code

In [the]: My_list = [1, 2, 3, 4, 6]in []: My_list.insert (4, 5) in []: my_listout[48]: [1, 2, 3, 4, 5, 6]

Note that the first parameter is the index, the second is the inserted value, and the value inserted in front of the index

You can also use slices to complete the above operations

In [Wuyi]: My_list = [1, 2, 3, 4, 6]in []: my_list[4:4] = [5]in []: my_listout[53]: [1, 2, 3, 4, 5, 6]

8.pop

Deletes an element, defaults to the last element, and finally returns the element

For example, the following code

In [si]: my_list = [1, 2, 3, 4, 5]in []: My_list.pop () out[55]: 5In []: my_listout[56]: [1, 2, 3, 4]in []: My_list.po P (0) out[57]: 1In [+]: my_listout[58]: [2, 3, 4]

Pop is the only list method that modifies the list and returns a value other than none.

Using pop to achieve a common data structure-stack (stack), this in the later article I will talk about, here do not elaborate

9.remove

Deletes the first element that is a specified value

For example, the following code

in [+]: word_list = [' to ', ' is ', ' or ', ' not ', ' to ', ' is ']in [max]: Word_list.remove (' to ') in [Max]: word_listout[61]: [' Be ', ' or ', ' not ', ' to ', ' being ']

10.reverse

Method reverse the elements in the list in reverse order

in [+]: my_list = [1, 2, 3, 4, 5]in []: My_list.reverse () in []: my_listout[64]: [5, 4, 3, 2, 1]

If you want to iterate the sequence in reverse order, you can use the function reversed. Instead of returning a list, this function returns an iterator (the iterator is described in detail in chapter 9th). You can use list to convert the returned object to a list.

For example, the following code

in [+]: my_list = [1, 2, 3, 4, 5]in []: List (Reversed (my_list)) out[66]: [5, 4, 3, 2, 1]

11.sort

Method sort is used to sort the list in place, but does not return a value

For example

In [the]: My_list = [7, 4, 3, 5, 8, 9, 1]in []: My_list.sort () in []: my_listout[70]: [1, 3, 4, 5, 7, 8, 9]

Because there is no return value, you can use the function sorted if you need to assign the sorted value to a variable conveniently.

in [+]: my_list = [7, 4, 3, 5, 8, 9, 1]in []: Other_list = sorted (my_list) in []: my_listout[73]: [7, 4, 3, 5, 8, 9, 1]in [All]: other_listout[74]: [1, 3, 4, 5, 7, 8, 9]

Note that for sort he has two optional parameters: Key and reverse

Key means the keywords you sort by

Reverse indicates whether to sort the list in reverse order, True or False

For example, the following two paragraphs of code

Key = Len

In [the]: word_list = [' Aardvark ', ' abalone ', ' Acme ', ' Add ', ' aerate ']in []: Word_list.sort (Key=len) in []: Word_listout [+]: [' Add ', ' Acme ', ' aerate ', ' abalone ', ' aardvark ']

Reverse = True

In [the]: My_list = [7, 4, 3, 5, 8, 9, 1]in []: My_list.sort (Reverse=true) in []: my_listout[80]: [9, 8, 7, 5, 4, 3, 1]

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13_python data type string strengthening _python programming path