%S usage in python

Detailed explanation and code examples of %S usage in Python

In Python, %S is a string formatting method used to format specified data The value is inserted into the string. The following will introduce the usage of %S in detail and give specific code examples.

Basic usage of %S:
%S is used to convert any type of data into a string and insert it into the placeholder in the string. In strings, placeholders are represented by %S. When the Python interpreter encounters %S, it replaces it with the string form of the corresponding data value.

Example 1:
name = "Tom"
age = 18
print("My name is %S, and I am %S years old." % (name, age) )
Output: My name is Tom, and I am 18 years old.

In example 1, the %S placeholder is replaced by the name and age variables respectively, and the values ​​of the name and age variables are respectively is the string "Tom" and the integer 18. Since %S converts data values ​​into string form, the name and age values ​​in the output results are presented in string form.

Advanced usage of %S:
%S can also be used with other placeholders to achieve more complex string formatting.

Example 2:
name = "Tom"
age = 18
height = 175.5
print("My name is %S, I am %d years old, and my height is %.1f cm." % (name, age, height))
Output: My name is Tom, I am 18 years old, and my height is 175.5 cm.

In example 2 , %d and %.1f respectively indicate formatting the age and height variables into integers and floating point numbers with one decimal place. In this way, in the output, age will be displayed as an integer, and height will be displayed as a floating point number with one decimal place.

In addition, %S can also be used to format multiple data values ​​and insert them in the specified order.

Example 3:
name1 = "Tom"
age1 = 18
name2 = "Jerry"
age2 = 20
print("The first person is %S, %d years old, and the second person is %S, %d years old." % (name1, age1, name2, age2))
Output: The first person is Tom, 18 years old, and the second person is Jerry, 20 years old.

In example 3, %S and %d are replaced by name1, name2 and age1, age2 respectively. In the output result, name1, name2 and age1, age2 are inserted into the corresponding positions in the specified order.

Notes on %S:
When using %S for string formatting, you need to pay attention to the matching of data types. If the placeholder for %S is an integer and a string is actually passed in, a runtime error may occur.

Example 4:
name = "Tom"
age = 18
print("My name is %S, and I am %d years old." % (name, age) )
Output: TypeError: %d format: a number is required, not str

In example 4, the type of the age variable is an integer, but when formatting the string, %S is used to express age. Since %S will convert the data value into a string form, when the age passed in is a string, a type mismatch error will occur.

In order to avoid this error, correct placeholders should be selected according to different data types to ensure the consistency of the data types.

To sum up, %S is a placeholder used for string formatting in Python, which is used to insert various types of data values ​​into strings. By rationally using %S, you can flexibly handle string formatting needs and make the code more concise and readable.

(Note: The above code examples are all written based on Python 3 version)

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