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This article mainly explains "how to use _ _ str__ and _ _ repr__ in python". Interested friends may wish to have a look at it. The method introduced in this paper is simple, fast and practical. Let's let the editor take you to learn how to use _ _ str__ and _ _ repr__ in python.

1. Introduction

When learning object-oriented, we know that there is a special method in python, called magic method. The characteristics of this method are as follows: 1. Methods are defined starting with two underscores and ending with two underscores, such as _ _ init__, _ _ str__, and _ _ repr__ 2. Generally speaking, this kind of method does not need to be called manually, it will be called automatically when a certain condition is met, and this condition can be called.

In Python, there are two magic methods used to describe object information, _ _ str__ and _ _ repr__,. So why define two such methods? in fact, they are designed for a different purpose: 1. The goal of _ _ repr__ is accuracy, or the result of _ _ repr__ is for the interpreter to use. 2. The goal of _ _ str__ is readability, or the result of _ _ str__ is for people to see.

two。 Analysis.

Next, let's take a detailed look at their usage: the output of the printed object is not very friendly without rewriting _ _ str__ and _ _ repr__, which is the memory address of the object, that is, the result of id.

# define Person class class Person (object): def _ _ init__ (self, name): self.name = namep = Person ("isaac")

The following are the results of the test output:

> print (p) > p > > p >

This output is not what we want, so we override the _ _ str__ and _ _ repr__ methods.

2.1 override _ _ str__ method # define Person class class Person (object): def _ init__ (self, name): self.name = namedef _ str__ (self): return "_ _ str__ method" + self.namep = Person ("isaac")

The following are the test results:

> print (p) _ str__ method isaac > str (p)'_ str__ method isaac' > f "{p}"'_ _ str__ method isaac' > p.incremental stringing _ ()'_ str__ method isaac' > p

At this point, we find that the _ _ str__ method is called when using print to print the object, to format the output of the object, and to call the str method. However, in the interactive environment, when the object is output directly, the _ _ str__ method is not called, and the output result is still the result of id.

2.2 rewrite _ _ repr__ method # define Person class class Person (object): def _ init__ (self, name): self.name = namedef _ str__ (self): return "_ _ str__ method" + self.namedef _ repr__ (self): return "_ _ repr__ method" + self.namep = Person ("isaac")

At this point, let's look at the result of the output.

> paired reprinters _ method isaac > p.incremental reprinters _ ()'_ _ repr__ method isaac' > print (p) _ str__ method isaac

Through a simple comparison, we find that in an interactive environment, the object is directly output and the _ _ repr__ method is called. It is also important to note that if you put the object in a container for output, the _ _ repr__ method is called.

> [p] [_ _ repr__ method isaac] > (p) _ _ repr__ method isaac > {"1": P} {'1procedures: _ _ repr__ method isaac} > print ([p]) [_ repr__ method isaac] so far, I believe you have a deeper understanding of "how to use the _ _ str__ and _ _ repr__ in python". You might as well do it in practice. Here is the website, more related content can enter the relevant channels to inquire, follow us, continue to learn!

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