如何使用打印在 python 中显示类实例

Question

我正在尝试打印类的实例，但是我得到的结果似乎是正确的格式，但不是我正在寻找的输出。

我已经按照某人的建议使用了defstr(self(，但我仍然得到相同的结果

这是整个代码：

class Employee:
empCount = 0
def __init__(self,name,salary):
self.name = name 
self.salary = salary
Employee.empCount += 1
def __str__(self):
print (self.name)
def displayCount(self):
print("Total Employee %d" % Employee.empCount)
def displayEmployee(self):
print ("Name : ", self.name, ", Salary: ",self.salary)
global emp1
global emp2
global n
global s
emp1 = ''
emp2 = ''
alist = [emp1,emp2]
alist_final =[]
for y in alist:
y = Employee('n',2)
alist_final.append(y)
y.displayEmployee()
print("Total Employee %d" % Employee.empCount)

print(alist_final)

这是我在命令行上得到的结果：

C:UsersDemiDesktopvirtuallearner>pr.py
z
2
Name :  z , Salary:  2
Total Employee 1
m
5
Name :  m , Salary:  5
Total Employee 2
[<__main__.Employee object at 0x0000022AFA278550>, <__main__.Employee object 
at 0x0000022AFA278550>]

我正在尝试打印出在 for 循环中所做的更改的实例

Answer 1

您可以使用__repr__方法，而不是使用__str__方法。使用此方法，无需将实例显式转换为字符串。查找代码：

class Employee:
empCount = 0
def __init__(self,name,salary):
self.name = name
self.salary = salary
Employee.empCount += 1
def __repr__(self):
return self.name
def displayCount(self):
print("Total Employee %d" % Employee.empCount)
def displayEmployee(self):
print ("Name : ", self.name, ", Salary: ",self.salary)
global emp1
global emp2
global n
global s
emp1 = ''
emp2 = ''
alist = [emp1,emp2]
alist_final =[]
for y in alist:
y = Employee('n',2)
alist_final.append(y)
y.displayEmployee()
print("Total Employee %d" % Employee.empCount)
print(alist_final)

输出如下所示：

Name :  n , Salary:  2
Total Employee 1
Name :  n , Salary:  2
Total Employee 2
[n, n]

希望这有帮助！

Answer 2

这里有两点需要注意。

1. 您没有调用实例的str方法。相反，您在容器上调用print，这是alist_final，这是一个列表。

   print(somelist)将调用str方法somelist，而不是list中的元素

2. 您没有返回字符串表示形式。取而代之的是，您用print来称呼它.

您需要从您实现的__str__方法中return表示形式，例如，

$ cat emp.py
class Employee:
empCount = 0
def __init__(self,name,salary):
self.name = name 
self.salary = salary
Employee.empCount += 1
def __str__(self):
return '{}(name={}, salary={})'.format(
self.__class__.__name__,
self.name,
self.salary)
def displayCount(self):
print("Total Employee %d" % Employee.empCount)
def displayEmployee(self):
print ("Name : ", self.name, ", Salary: ",self.salary)

alist_final =[]
for _ in range(2):
y = Employee('n',2)
alist_final.append(y)
y.displayEmployee()
print("Total Employee %d" % Employee.empCount)
print([str(x) for x in alist_final])

输出：

$ python emp.py
('Name : ', 'n', ', Salary: ', 2)
Total Employee 1
('Name : ', 'n', ', Salary: ', 2)
Total Employee 2
['Employee(name=n, salary=2)', 'Employee(name=n, salary=2)']

Answer 3

添加__repr__方法，该方法将在类的实例传递到 print 函数时运行。

def __repr__(self) -> str:
return f"employee<{name: {self.name}, salary: {self.salary}>"