Effective use of the len() function in Python

How to correctly use the len function in Python requires specific code examples

In Python programming, the len function is a very commonly used function. It can be used to get the length or number of elements of an iterable object. The use of the len function is very simple, but in actual applications, some tips on using the len function correctly may make your code more efficient, concise and readable. This article will explain in detail how to use the len function correctly and provide specific code examples.

1. Get the length of a string
   String is one of the commonly used data types in Python. Getting the length of a string is one of the most common uses of the len function. The following is a sample code to get the length of a string:

string = "Hello World"
length = len(string)
print("字符串的长度为：", length)

The output result is: the length of the string is: 11

2. Get lists, tuples, sets, dictionaries The length
   In addition to strings, the len function can also be used to obtain the length of container types such as lists, tuples, sets, and dictionaries. The specific code example is as follows:

list1 = [1, 2, 3, 4, 5]
length1 = len(list1)
print("列表的长度为：", length1)

tuple1 = (1, 2, 3, 4, 5)
length2 = len(tuple1)
print("元组的长度为：", length2)

set1 = {1, 2, 3, 4, 5}
length3 = len(set1)
print("集合的长度为：", length3)

dict1 = {"name": "Alice", "age": 20, "gender": "female"}
length4 = len(dict1)
print("字典的长度为：", length4)

The output result is:
The length of the list is: 5
The length of the tuple is: 5
The length of the set is: 5
The length of the dictionary is: 3

3. Get the number of rows and columns of a two-dimensional list
   For a two-dimensional list (nested list within a list), we can get its number of rows through the len function and the number of columns, respectively used to represent the outer length and inner length of the two-dimensional list. The following is a sample code to obtain the number of rows and columns of a two-dimensional list:

matrix = [[1, 2, 3], 
          [4, 5, 6], 
          [7, 8, 9]]
row = len(matrix)
column = len(matrix[0])
print("二维列表的行数为：", row)
print("二维列表的列数为：", column)

The output result is:
The number of rows of the two-dimensional list is: 3
The columns of the two-dimensional list The number is: 3

4. Get the number of valid characters in the string
   When processing strings, sometimes we need to exclude some invalid characters (such as spaces, tabs, etc.), just Count the number of valid characters. We can achieve this function with the help of the len function and some string processing methods. The following is a sample code to obtain the number of valid characters in a string:

string = "Hello World"
count = 0
for char in string:
  if char != ' ':
    count += 1
print("字符串中的有效字符个数为：", count)

The output result is: the number of valid characters in the string is: 10

Through the above sample code , we can use the len function correctly to get the length of strings, lists, tuples, sets, dictionaries and two-dimensional lists. At the same time, we also learned how to get the number of valid characters in a string. Proper use of the len function can make our code more efficient, concise and readable.

Summary: Understanding the purpose and usage of the len function is very important for Python programming. Whether it is to get the length of a string or the number of elements of a container type, the len function can help us achieve it easily. In daily programming, reasonable use of the len function can improve code efficiency and increase code readability.

The above is an introduction and code examples on how to correctly use the len function in Python. Hope this helps!

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