class fileDetails :
def __init__(self,host,usr,pwd,database):
self.host=host
self.usr.usr
self.pwd=pwd
self.database=database
def __init__(self,connection,sql,path):
self.connection=mysql_connection()
self.sql=sql
self.path=path
If I use the constructor then it gives an error:
onnetction = fileDetails('localhost',"root","",'bulsorbit')
TypeError: __init__() takes exactly 4 arguments (5 given)
The overloading of the constructor (or any other function) is not allowed in python. So you cannot define two __init__ functions for your class.
You can have a look to this post or this one
The main ideas are to use default values or to create 'alternate constructors' or to check the number and the type of your args in order to choose which method to apply.
def __init__(self, **args):
Then args will be a dictionary containing all the parameters. So you will be able to make the difference between
connection = fileDetails(host='localhost',usr="root",pwd="",database='bulsorbit')
and
connection = fileDetails(connection="...",sql="...",path="...")
Define a single constructor with optional arguments.
def __init__(self,host='host',usr='user',pwd='pwd',database='db',connection=None,sql=None,path=None):
if connection:
# however you want to store your connection
self.sql=sql
self.path=path
else:
self.host=host
self.usr.usr
self.pwd=pwd
self.database=database
Or something of the sort.
maybe you can use len() to choose the right branch:
class Foo(object):
def __init__(self, *args):
if len(args) == 4: # network
self.host = args[0]
self.user = args[1]
self.pwd = args[2]
self.database = args[3]
elif len(args) == 3: # database
self.connection = mysql_connection() # maybe it's args[0]?
self.sql = args[1]
self.path = args[2]
def main():
foo = Foo('localhost',"root","",'bulsorbit')
print foo.host
if __name__ == "__main__":
main()
# output
# localhost
but, sine Explicit is better than implicit. maybe this is workable too:
class Foo(object):
def __init__(self, initdata):
if initdata['style'] == 'network':
self.host = initdata['host']
self.usr = initdata['usr']
self.pwd = initdata['pwd']
self.database = initdata['database']
elif initdata[style] == 'database':
self.connection = mysql_connection()
self.sql = initdata['sql']
self.path = initdata['path']
def main():
data = dict({'style': 'network',
'host': 'localhost',
'usr': 'root',
'pwd': '',
'database': 'database'})
foo = Foo(data)
print foo.host
if __name__ == "__main__":
main()
# output
# localhost
In Python the functions in a class are stored internally in a dictionary (remember that constructors are just regular functions), and so only one function of the same name can exist. Therefore, when defining more than one functions with the same name the last one will overwrite all the previously defined ones and you'll end up with only one function.
I suggest you look into keyword and default arguments to see the proper way of achieving what you want.
Here's one way to achieve this:
class FileDetails:
def __init__(self, *args, **kwargs):
if len(args) == 3:
self.conn, self.sql, self.path = args
elif len(args) == 4:
self.host, self.usr, self.pw, self.db = args
else:
# handle appropriately
fd1 = FileDetail('connstring', 'select * from foo', '/some/path')
print fd1.conn, fd1.sql, fd1.path
fd2 = FileDetail('host', 'user', 'pass', 'somedb')
print fd2.conn, fd2.usr, fd2.pw, fd2.db
Of course, you should do the appropriate type checking and error handling in the constructor.
On the side note: if you really, really, reallllllyyy must do JiP (Java in Python) then multiple dispatch methods are possible with some additional code eg. here and even beter: here by BDFL.
Personally I try to avoid using them.
__init__is NOT a constructor method. Python has dedicated constructor method__new__, which is hardly used in everyday programming.