Little knowledge you must master--detailed explanation of Python len examples

Description

The Python len() method returns the length or number of items of an object (character, list, tuple, etc.).

Syntax

len() method syntax:

len( s )

Return value

Returns the length of the object.

Example

The following example shows the use of len():

>>>str = "runoob">>> len(str)             # 字符串长度6>>> l = [1,2,3,4,5]>>> len(l)               # 列表元素个数5

len is called when calling len(instance). len is a built-in function that returns the length of an object. It can be used for any object that is thought to have a deserving length.

The len of a string is the number of its characters; the len of a dictionary is the number of its keywords; the len of a list or sequence is the number of elements. For class instances, define the len method, and then compile it yourself...

In SQLite3, to query the number of results of the select statement, you cannot directly use the len(res) statement. You need to assign the fetchall method of the cursor to a array, and then use the len method on the data. The specific examples are as follows:

   import sqlite3
        conn = sqlite.connect('test.db')    cursor = conn.cursor()    cursor.execute("select uid, username, userpwd from member")    records = cursor.fetchall()
    num = len(records)

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