Why I'm getting this error?
local variable 'type' referenced before assignment
Code:
try:
if type(meeting.modified_date) != bool:
//code
except Exception as e:
raise ValidationError(_(str(e)))
finally:
type = None
if 1:
type = 'auto'
else:
type = 'manual'
I was think some local variable creating this error but after debugging I come to know that this if condition creating an error because of this type().
Empty values on record attributes in Odoo recordsets will always be falsy, except for number fields like float or integer. They will have the value zero and this also is falsy, but zero values can have a meaning in some contexts, so you should always think about the if conditions when checking number values.
Anyways, you can just change your if condition to
if meeting.modified_date:
, because non set date fields are falsy and set date fields are truthy.
One way to get that error.
def _something(self, meeting):
if type(meeting.modified_date) != bool:
pass
#rename it
type = "small"
Edit:
try:
if type(meeting.modified_date) != bool:
//code
except Exception as e:
raise ValidationError(_(str(e)))
finally:
#this is local variable and the fix is
record_type = None
if 1:
record_type = 'auto'
else:
record_type = 'manual'
#and later where type is used it should renamed aswell
The reason you are getting this error is because you assign the global function type to a value in your code. If you do this, then the global function type will be overwritten to be a variable even before the actual assignment in the scope of the name space. Because the python interpreter now treats type as a local variable instead of the global function it is not assigned when you try to call the global function (which is treated as a local variable).
Solution: do not assign names of global functions to variables and rename the variable "type" to something else e.g., object_type.
I mean the code example is basically provided by #Paxmees in the replies. His explanation is a bit difficult to understand. But if you want to see one:
def example_error(var):
if type(var) == bool:
pass
#this produces the error, because you overwrite global function type
type = "string"
def example_fixed(var):
if type(var) == bool:
pass
#fixed do not overwrite global function type:
type_of_var = "string"
Here is my task:
Write a function get_value(dictionary, key) which returns the value for the given key in the given dictionary, using the get method. If the key is not valid, your function should return -1.
I have written a function which assesses a dictionary using a get function and the code work just fine. However, I need a way to return a value of -1 of the key is not valid instead of returning "Not a Key". I have been requested to solve this issue without the use of an if statement. Here is my current code:
def get_value(dictionary, key):
for key in key.split("."):
dictionary.get(key)
dictionary = dictionary[key]
return dictionary
Thanks in advance.
I am new to Python, stupid question ahead
I need to compare the entries from a MySQL database with ldap. I created a dictionary to hold the corresponding values, when I try to loop through the dictionary and pass them to ldap3 entries to show the results it takes the variable as literal.
for x in values_dict:
value2=values_dict[x]
try:
ldap_conn.entries[0].value2
except Exception as error:
print(error)
else:
print(value2)
attribute 'value2' not found
If I replace value2 with 'sn' or any of the other attributes I have pulled it works fine. I have also played around with exec() but this returns nothing.
for x in values_dict:
value2=values_dict[x]
test1='ldap_conn.entries[0].{}'.format(value2)
try:
result1=exec(test1)
except Exception as error:
print(error)
else:
print(result1)
None
Any ideas?
EDIT 1 : As requested here are the values for values_dict. As stated previously the loop does parse these correctly, ldap does return the attributes, but when I try to use a variable to lookup the attributes from entries the variable is taken literally.
values_dict = {
"First_Name": "givenname",
"Middle_Name": "middlename",
"Last_Name": "sn",
"Preferred_Name": "extensionattribute2",
"Work_Location": "physicaldeliveryofficename",
"Work_City": "l",
"Work_State": "st",
"Work_Postal": "postalcode",
"Work_Email": "mail"
}
The syntax somevariable.someattr, which you are using here:
ldap_conn.entries[0].value2
Always means "access an attribute named someattr of somevariable". It's always interpreted as a literal string. If you need to dynamically access an attribute, use the getattr function:
getattr(ldap_conn.entries[0], value2)
You're not currently assigning that that result anywhere, so you probably want something like:
result1 = getattr(ldap_conn.entries[0], value2)
I am new to Python and am at a lost as to what I'm doing wrong. I am trying to use the fqdn variable that is being returned to the caller which is main() but I'm getting NameError: name 'fqdn' is not defined
I'm betting this is some type of global variable statement issue or something like that, but I've been researching this and can't figure it out.
If a function from a module returns a value, and the caller is main(), shouldn't main() be able to use that returned value???
Here's the layout:
asset.py
def import_asset_list():
# Open the file that contains FQDNs
openfile = open(r"FQDN-test.txt")
if openfile.mode == 'r':
# Remove CR from end of each item
fqdn = openfile.read().splitlines()
# Add https to the beginning of every item in list
fqdn = ["https://" + item for item in fqdn]
openfile.close()
return fqdn
tscan.py
def main():
import asset
asset.import_asset_list()
# Iterate through list
for i in fqdn:
if SCHEDULED_SCAN == 1:
create_scheduled_scan(fqdn)
launch_scan(sid)
check_status_scan(uuid)
else:
create_scan(fqdn)
launch_scan(sid)
check_status_scan(uuid)
Short Explanation
Yes, main() should be able to use the returned value, but it's only the value that is returned, not the variable name. You have to define a variable of your own name, to receive the value, and use that instead.
Long Explanation
The name of a variable inside any function is simply a "label" valid only within the scope of this function. A function is an abstraction which means "Give me some input(s), and I will give you some output(s)". Within the function, you need to reference the inputs somehow and, potentially, assign some additional variables to perform whatever it is you would like to. These variable names have no meaning whatsoever outside the function, other than to, at most, convey some information as to the intended use of the function.
When a function returns a value, it does not return the "name" of the variable. Only the value (or the reference in memory) of the variable. You can define your own variable at the point where you call the function, give it your own name and assign to it the returned result of the function, so you simply have to write:
def main():
import asset
my_asset_list = asset.import_asset_list()
# Iterate through list
for i in my_asset_list:
if SCHEDULED_SCAN == 1:
create_scheduled_scan(my_asset_list)
launch_scan(sid)
check_status_scan(uuid)
else:
create_scan(my_asset_list)
launch_scan(sid)
check_status_scan(uuid)
I don't know where the uuid and the sid variables are defined.
To make sure you have understood this properly, remember:
You can have multiple functions in the same file, and use identically-named variables within all those functions, this will be no problem because a variable (with its name) only exists within each specific function scope.
Variable names do not "cross" the boundaries of the scope, only variable values/references and to do this, a special construct is used, i.e. the return [something] statement.
I need a way to get a dictionary value if its key exists, or simply return None, if it does not.
However, Python raises a KeyError exception if you search for a key that does not exist. I know that I can check for the key, but I am looking for something more explicit. Is there a way to just return None if the key does not exist?
You can use dict.get()
value = d.get(key)
which will return None if key is not in d. You can also provide a different default value that will be returned instead of None:
value = d.get(key, "empty")
Wonder no more. It's built into the language.
>>> help(dict)
Help on class dict in module builtins:
class dict(object)
| dict() -> new empty dictionary
| dict(mapping) -> new dictionary initialized from a mapping object's
| (key, value) pairs
...
|
| get(...)
| D.get(k[,d]) -> D[k] if k in D, else d. d defaults to None.
|
...
Use dict.get
Returns the value for key if key is in the dictionary, else default. If default is not given, it defaults to None, so that this method never raises a KeyError.
You should use the get() method from the dict class
d = {}
r = d.get('missing_key', None)
This will result in r == None. If the key isn't found in the dictionary, the get function returns the second argument.
If you want a more transparent solution, you can subclass dict to get this behavior:
class NoneDict(dict):
def __getitem__(self, key):
return dict.get(self, key)
>>> foo = NoneDict([(1,"asdf"), (2,"qwerty")])
>>> foo[1]
'asdf'
>>> foo[2]
'qwerty'
>>> foo[3] is None
True
I usually use a defaultdict for situations like this. You supply a factory method that takes no arguments and creates a value when it sees a new key. It's more useful when you want to return something like an empty list on new keys (see the examples).
from collections import defaultdict
d = defaultdict(lambda: None)
print d['new_key'] # prints 'None'
A one line solution would be:
item['key'] if 'key' in item else None
This is useful when trying to add dictionary values to a new list and want to provide a default:
eg.
row = [item['key'] if 'key' in item else 'default_value']
As others have said above, you can use get().
But to check for a key, you can also do:
d = {}
if 'keyname' in d:
# d['keyname'] exists
pass
else:
# d['keyname'] does not exist
pass
You could use a dict object's get() method, as others have already suggested. Alternatively, depending on exactly what you're doing, you might be able use a try/except suite like this:
try:
<to do something with d[key]>
except KeyError:
<deal with it not being there>
Which is considered to be a very "Pythonic" approach to handling the case.
For those using the dict.get technique for nested dictionaries, instead of explicitly checking for every level of the dictionary, or extending the dict class, you can set the default return value to an empty dictionary except for the out-most level. Here's an example:
my_dict = {'level_1': {
'level_2': {
'level_3': 'more_data'
}
}
}
result = my_dict.get('level_1', {}).get('level_2', {}).get('level_3')
# result -> 'more_data'
none_result = my_dict.get('level_1', {}).get('what_level', {}).get('level_3')
# none_result -> None
WARNING: Please note that this technique only works if the expected key's value is a dictionary. If the key what_level did exist in the dictionary but its value was a string or integer etc., then it would've raised an AttributeError.
I was thrown aback by what was possible in python2 vs python3. I will answer it based on what I ended up doing for python3. My objective was simple: check if a json response in dictionary format gave an error or not. My dictionary is called "token" and my key that I am looking for is "error". I am looking for key "error" and if it was not there setting it to value of None, then checking is the value is None, if so proceed with my code. An else statement would handle if I do have the key "error".
if ((token.get('error', None)) is None):
do something
You can use try-except block
try:
value = dict['keyname']
except IndexError:
value = None
d1={"One":1,"Two":2,"Three":3}
d1.get("Four")
If you will run this code there will be no 'Keyerror' which means you can use 'dict.get()' to avoid error and execute your code
If you have a more complex requirement that equates to a cache, this class might come in handy:
class Cache(dict):
""" Provide a dictionary based cache
Pass a function to the constructor that accepts a key and returns
a value. This function will be called exactly once for any key
required of the cache.
"""
def __init__(self, fn):
super()
self._fn = fn
def __getitem__(self, key):
try:
return super().__getitem__(key)
except KeyError:
value = self[key] = self._fn(key)
return value
The constructor takes a function that is called with the key and should return the value for the dictionary. This value is then stored and retrieved from the dictionary next time. Use it like this...
def get_from_database(name):
# Do expensive thing to retrieve the value from somewhere
return value
answer = Cache(get_from_database)
x = answer(42) # Gets the value from the database
x = answer(42) # Gets the value directly from the dictionary
If you can do it with False, then, there's also the hasattr built-in funtion:
e=dict()
hasattr(e, 'message'):
>>> False