Tutorial by Examples: n

The math-module contains another math.pow() function. The difference to the builtin pow()-function or ** operator is that the result is always a float: import math math.pow(2, 2) # 4.0 math.pow(-2., 2) # 4.0 Which excludes computations with complex inputs: math.pow(2, 2+0j) TypeErro...

Both the math and cmath-module contain the Euler number: e and using it with the builtin pow()-function or **-operator works mostly like math.exp(): import math math.e ** 2 # 7.3890560989306495 math.exp(2) # 7.38905609893065 import cmath cmath.e ** 2 # 7.3890560989306495 cmath.exp(2) # (...

The math module contains the expm1()-function that can compute the expression math.e ** x - 1 for very small x with higher precision than math.exp(x) or cmath.exp(x) would allow: import math print(math.e ** 1e-3 - 1) # 0.0010005001667083846 print(math.exp(1e-3) - 1) # 0.0010005001667083846 p...

Supposing you have a class that stores purely integer values: class Integer(object): def __init__(self, value): self.value = int(value) # Cast to an integer def __repr__(self): return '{cls}({val})'.format(cls=self.__class__.__name__, ...

A basic Employees table, containing an ID, and the employee's first and last name along with their phone number can be created using CREATE TABLE Employees( Id int identity(1,1) primary key not null, FName varchar(20) not null, LName varchar(20) not null, PhoneNumber varchar(10)...

Click the Run button in the toolbar (or press ⌘R) to build & run your project. Click Stop (or press ⌘.) to stop execution.   Click & hold to see the other actions, Test (⌘U), Profile (⌘I), and Analyze (⇧⌘B). Hold down modifier keys ⌥ option, ⇧ shift, and ⌃ control for more variants.  ...

A submodule references a specific commit in another repository. To check out the exact state that is referenced for all submodules, run git submodule update --recursive Sometimes instead of using the state that is referenced you want to update to your local checkout to the latest state of that s...

You can have multiple versions of Xcode installed at the same time (including beta versions). Simply rename the application in Finder to avoid conflicts. Note: Installing Xcode from the App Store will tend to overwrite an existing version on your machine. You can also install Xcode from a direct ...

CREATE TABLE HR_EMPLOYEES ( PersonID int, LastName VARCHAR(30), FirstName VARCHAR(30), Position VARCHAR(30) ); CREATE TABLE FINANCE_EMPLOYEES ( PersonID INT, LastName VARCHAR(30), FirstName VARCHAR(30), Position VARCHAR(30) ); Let's say we want to ...

You can list existing git aliases using --get-regexp: $ git config --get-regexp '^alias\.' Searching aliases To search aliases, add the following to your .gitconfig under [alias]: aliases = !git config --list | grep ^alias\\. | cut -c 7- | grep -Ei --color \"$1\" "#" The...

String also have an index method but also more advanced options and the additional str.find. For both of these there is a complementary reversed method. astring = 'Hello on StackOverflow' astring.index('o') # 4 astring.rindex('o') # 20 astring.find('o') # 4 astring.rfind('o') # 20 The ...

All built-in collections in Python implement a way to check element membership using in. List alist = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] 5 in alist # True 10 in alist # False Tuple atuple = ('0', '1', '2', '3', '4') 4 in atuple # False '4' in atuple # True String astring = 'i am a s...

list and tuple have an index-method to get the position of the element: alist = [10, 16, 26, 5, 2, 19, 105, 26] # search for 16 in the list alist.index(16) # 1 alist[1] # 16 alist.index(15) ValueError: 15 is not in list But only returns the position of the first found element: ...

dict have no builtin method for searching a value or key because dictionaries are unordered. You can create a function that gets the key (or keys) for a specified value: def getKeysForValue(dictionary, value): foundkeys = [] for keys in dictionary: if dictionary[key] == value: ...

Sorted sequences allow the use of faster searching algorithms: bisect.bisect_left()1: import bisect def index_sorted(sorted_seq, value): """Locate the leftmost value exactly equal to x or raise a ValueError""" i = bisect.bisect_left(sorted_seq, value) ...

Searching in nested sequences like a list of tuple requires an approach like searching the keys for values in dict but needs customized functions. The index of the outermost sequence if the value was found in the sequence: def outer_index(nested_sequence, value): return next(index for index, ...

Let's say we have a query of the remaining horsemen that needs to populate a Person class. NameBornResidenceDaniel Dennett1942United States of AmericaSam Harris1967United States of AmericaRichard Dawkins1941United Kingdom public class Person { public string Name { get; set; } public int...

Let's look at a more complex example that contains a one-to-many relationship. Our query will now contain multiple rows containing duplicate data and we will need to handle this. We do this with a lookup in a closure. The query changes slightly as do the example classes. IdNameBornCountryIdCountry...

Sometimes the number of types you are mapping exceeds the 7 provided by the Func<> that does the construction. Instead of using the Query<> with the generic type argument inputs, we will provide the types to map to as an array, followed by the mapping function. Other than the initial ma...

If the query column names do not match your classes you can setup mappings for types. This example demonstrates mapping using System.Data.Linq.Mapping.ColumnAttributeas well as a custom mapping. The mappings only need to be setup once per type so set them on application startup or somewhere else ...