Python is an interpreted, object-oriented, high-level programming language with dynamic semantics. Its high-level built in data structures, combined with dynamic typing and dynamic binding, make it very attractive for Rapid Application Development, as well as for use as a scripting or glue language to connect existing components together.
Basics
Table of Contents
display
print("hello world")
Code language: Python (python)
comments
#
is used to comment a line in Python
Data Types
Category | Data Type |
---|---|
Text | str |
Number | int, float, complex |
Boolean | bool |
Binary | bytes, bytearray, memoryview |
Set | set, frozenset |
Sequence | list, tuple, range |
Mapping | dict |
- type() is used to know the data type of a variable
Data casting
Constructor function | desc |
---|---|
int() | constructs an integer from any form of data like string, float or integer |
float() | constructs a float number from any form of data like string, float or integer |
str() | constructs a string from any form of data like string, float or integer |
Variables
In Python, declaring variables is not required. Means you don’t need to specify whether it is an integer or string etc as Python is a dynamically typed language.
Operators
Type | Operators |
---|---|
Arithmetic Operators | + – * / % ** // |
Comparision Operators | == != > >= < <= |
Bitwise Operators | & ^ | ^ ~ << >> |
Logical Operators | && || ! |
Assignment Operators | = += -= *= /= %= **= //= |
Membership Operators | in, not in |
Identity Operators | is, is not |
Functions
# declaring a function
def function-name(parameters):
statement(s)
#here parameters are optional
#code
function-name(parameters)
#calling a function
Code language: Python (python)
Example
def my_func():
x = 10
print("Value inside function:",x)
x = 20
my_func()
print("Value outside function:",x)
Code language: PHP (php)
Collections
1. List
List is ordered collection of items and can be changed. []
are used to represent lists.
Example
mylist=["iPhone","Pixel","Samsung"]
print(mylist[0]) # prints iPhone
print(mylist[7]) # throws IndexError : list index out of range
print(mylist[-1]) # prints Samsung
Code language: Python (python)
Operations
Operation | Description |
---|---|
lst.append(val) | add an item to list at end |
lst.extend(seq) | add sequence of items to list at end |
lst.insert(index,val) | insert an item at given index |
lst.remove(val) | remove first item with value val |
lst.pop([index] )→value | remove & return item at index |
lst.sort() | sort the given list items |
lst.reverse() | reverse the given list items |
2. Tuple
Tuple is ordered collection of items and can’t be changed. ()
are used to represent Tuples.
Example
myTuple = ["iPhone","Pixel","Samsung"]
print(myTuple[0]) # prints iPhone
print(myTuple[7]) # throws IndexError: tuple index out of range
print(myTuple[-1]) # prints Samsung
Code language: Python (python)
3. Set
Set is unordered collection of items and it is unindexed. {}
are used to represent sets.
Example
mySet = {"iPhone", "Pixel", "Samsung"}
mySet.add('OnePlus')
print(mySet) # prints {'iPhone', 'Samsung', 'OnePlus', 'Pixel'}
Code language: Python (python)
Operations
Method | Description | Usage |
---|---|---|
add() | to add an element to the set | mySet.add(‘value’) |
clear() | to remove all the elements from the set | mySet.clear() |
pop() | to remove last element from the set | mySet.pop() |
remove() | to remove a specified element from the set | mySet.remove(“value”) |
del() | to delete a set | del myset |
copy() | to return a copy of the set | copySet = mySet.copy() |
union() | to return a set containing the union of sets | mySet3 = mySet1.union(mySet2) |
update() | to update the set with the union of this set and others | mySet1.update(mySet2) |
4. Dictionary
Dictionary is a collection of key value pairs which is unordered, can be changed, and indexed. They are written in curly brackets with key – value pairs.
Example
mydict = {
"brand" :"iPhone",
"model": "iPhone 11"
}
val = mydict["brand"]
print(val) # prints iPhone
Code language: Python (python)
Operation | Description |
---|---|
d[key] =value | To add a new key-value pair to dictionary or to change it’s value if key is existing |
d.copy() | Returns a copy of the dictionary |
d.keys() | Returns a list containing all the dictionary’s keys |
d.values() | Returns a list of all the values in the dictionary |
d.items() | Removes the element with the specified key |
d.clear() | To empty the dictionary items. |
del d[key] | To remove an item from a dictionary. |
d.pop(key) | To remove an item from a dictionary. |
d.popitem() | To removes the item that was last inserted into the dictionary |
d.get(key) | Returns the value of the specified key |
d.setdefault(key) | Returns the value of the specified key. If the key does not exist then returns the default value provided |
Conditional Statements
1. If
if conditional-expression :
#code
Code language: Python (python)
2. If-else
if conditional-expression :
#code
else :
#code
Code language: Python (python)
3. Nested-If-else
if conditional-expression :
#code
elif conditional-expression :
#code
else :
#code
Code language: Python (python)
Loops
1. For
For loop is used to iterate over arrays(list, tuple, set, dictionary) or strings.
Syntax
for variable in arrays :
#code
Code language: CSS (css)
2. While
while condition
#code
Code language: PHP (php)
Useful String Methods
str.strip() | str.lower() | str.upper() |
str.replace(“str to be replaced”,”new string to replace”) | str.split(“seperator”) | len(str) |
+ for concatenation | str.count(substr) | str.find(substr) |
str.index(substr, start, end) | str.join(array) | str.partition(substr) |
str.zfill(len) | str.swapcase() | str.isdecimal() |
str.isdigit() | str.islower() | str.isupper() |
str.endswith(value, start, end) | str.startswith(value, start, end) | str.isspace() |
Python with Mongodb
Install a python driver pymongo
to connect with MongoDB.
Create Database
import pymongo
db = pymongo.MongoClient("mongodb://localhost:27017/")
mydb = db["sample"]
Code language: Python (python)
Create collection
import pymongo
db = pymongo.MongoClient("mongodb://localhost:27017/")
mydb = db["sample"]
mycln = mydb["details"]
Code language: Python (python)
Insert
<em>#insert a single document</em>
doc = mycln.insert_one(mydict)
# insert multiple documents
mylist =[
{"name": "foo", "age": 20},
{"name": "bar", "age": 25},
{"name": "apple", "age": 30}
]
doc1 = mycln.insert_many(mylist)
Code language: Python (python)
Read
#to return all the documents
<strong>for</strong> doc <strong>in</strong> mycln.find():
print(doc)
# to return first occurence
doc1=mycln.find_one()
print(doc1)
Code language: Python (python)
Update
# to update a single document
mycln.update_one({"name" : "foo"}, {"$set":{"age": 23}})
Code language: Python (python)
Delete
# to delete a single document
doc1 = mycln.delete_one({"name" : "foo"})
Code language: Python (python)
Python with Files
Create
Use open() function with c
or a
or w
as mode.
file = open("myfile.txt","c")
Code language: Python (python)
Read
Use open() function with r
as mode.
file = open("myfile.txt","r")
print(file.read())
Code language: Python (python)
Update or Append
Use open() function with a
or w
as mode.
file = open("myfile.txt","a")
file.write("Happy learning!!")
file.close()
Code language: Python (python)
Delete
For deleting files, you must import os module and use os.remove()
function.
import os
os.remove(filename)
Code language: Python (python)
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