Data types in Python

Generally for any technology to understand or work as a beginner we need to understand the types/input predefined instruction of the language platform we start working. In this we will discuss the type with calling and code snippet for Data types in Python which includes inbuilt primitives and structured:

For details You can also visit Operators-in-Python

1. dictionary
2. list
3. tupples
4. factors (we will avoid these, but they have their uses)
5. logical
6. integer
7. numeric
8. complex
9. character

 Dictionaries

A dictionary is built in data type of Python which are indexed by keys, which can be any immutable type, strings and numbers can always be keys. A dictionary are storing a value with some key and extracting the value given the key.

Syntax         Meaning

D1 = { }     Empty dictionary

D2 = {'Ax': 2, 'Bn': 3}    Two-item dictionary

D2['session']         Indexing by key

D2.has_key('UserName'),         UserName' in D2 membership test

D2.keys( ), D2.values( ), D2.items( ) lists of keys, values, items

D2.copy( ), D2.update(D1)       shallow copy, dict merging

D2.get(key, default=None)      "indexing" w/default value

len(D1)       Length (number stored entries)

D2[key] =300       Adding/changing

del D2[key] deleting

D4 = dict(zip(klist, vlist))         Construction

List

A list is Python-object which can contain many different types of elements inside it. This can be created using [] bracket .

# Empty

Command::  dList =[]

Some of the important command used to manipulate/operate upon the list as below-

dList.count(x)       Returns the number of occurrences of x in dList

dList.index(x)        Returns the index of the first occurrence of x in dList or raises an exception if dList has no such item

dList.append(x)     Appends x to the end of dList

dList.extend(l)      Appends all the items of list dList to the end of dList

dList.insert(i,x)      Inserts x at index i in dList

dList.remove(x)     Removes the first occurrence of x from dList

dList.pop(i=-1)      Returns the value of the item at index i and removes it from dList

dList.reverse( )      Reverses, in-place, the items of dList

dList.sort(f=cmp)  Sorts, in-place, the items of dList, comparing items by f

 

Tuple

A tuple is a sequence of values similar to a list. The values stored in a tuple can be any type, and they are indexed by integers. Difference between tuples and list as tuples are immutable. Tuples are also comparable and hash-table so we can sort lists of them and use tuples as key values in Python dictionaries..

# Empty

Command::  dtple =()

Some of the important command used to manipulate/operate upon the list as below-

( )      An empty tuple

dtple = (0,) A one-item tuple (not an expression)

dtple 2 = (0, 'Ni', 1.2, 3) A four-item tuple

dtple 2 = 0, 'Ni', 1.2, 3    Another four-item tuple (same as prior line)

dtple[i]        Indexing

dtple[i:j]      slicing

len(dtple)    length (number of items)

dtple + dtple2       Concatenation

dtple2 * 3    repetition

for x in dtple2       Iteration

3 in dtple2   membership

Some of the inbuilt data types

`expr,...`     String conversion

{key:expr,...}       Dictionary creation

[expr,...]      List creation

(expr,...)      Tuple creation or simple parentheses

f(expr,...)     Function call

x[index:index]      Slicing

x[index]      Indexing

x.attr Attribute reference

x**y  Exponentiation (x to yth power)

~x     Bitwise NOT

+x, -x          Unary plus and minus

x*y, x/y, x//y, x%y         Multiplication, division, remainder

x+y, x-y      Addition, subtraction

x<<y, x>>y Left-shift, right-shift

x&y    Bitwise AND

x^y    Bitwise XOR

x|y     Bitwise OR

x<y, x<=y, x>y, x>=y    Comparisons

x<>y, x!=y, x==y Equality/inequality tests*

x is y, x is not y     Identity tests

x in y, x not in y    Membership tests

not x  Boolean NOT

x and y        Boolean AND

x or y Boolean OR

lambda arg,...: expr        Anonymous simple function