Is it possible to alter attributes of instances during its initialization?

E. G the following code.

class Sensor() :
 def __init__(self) :
 self.name = 'pressure' 

Sensor1 = Sensor(name='pH') 

Would that be possible?

You need to explicitly declare you accept a name argument and then you need to explicitly update the appropriate attribute:

class Sensor():
 def __init__(self, name='pressure'):
 self.name = name

Notice that I'm using 'pressure' as a default value for the name argument in case the consumer does not provide it:

a = Sensor()
print(a.name) # 'pressure'

b = Sensor(name='sensor')
print(b.name) # 'sensor'

name can also be provided as a positional argument:

c = Sensor('some_name')
print(c.name) # 'some_name'

A more generic approach

There's also a more generic approach (if the use cases requires it), which involves creating the attributes dynamically:

class Sensor():
 def __init__(self, **kwargs):
 for attr, value in kwargs.items():
 setattr(self, attr, value)

Then you can do something like:

d = Sensor(name='foo', temperature=70, active=True)
print(d.name) # 'foo'
print(d.temperature) # 70
print(d.active) # True

Not like that, if you want to set the attribute you would have to do something like:

class Sensor() :
 def __init__(self, name='pressure') :
 self.name = name 

Sensor1 = Sensor(name='pH')

If not provided the name would be pressure but if name is given in the initialization it will be set to the one provided.

You will need to give a way to pass those and set default values. In your example, you just need to add a default.

 class Sensor() :
 def __init__(self,name='pressure') :
 self.name = name