Table of Contents
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
display
print("hello world")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 functionExample
def my_func():
x = 10
print("Value inside function:",x)
x = 20
my_func()
print("Value outside function:",x)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 SamsungOperations
| 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 Samsung3. 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'}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| 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 :
#code2. If-else
if conditional-expression :
#code
else :
#code3. Nested-If-else
if conditional-expression :
#code
elif conditional-expression :
#code
else :
#codeLoops
1. For
For loop is used to iterate over arrays(list, tuple, set, dictionary) or strings.
Syntax
for variable in arrays :
#code2. While
while condition
#code 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"]Create collection
import pymongo
db = pymongo.MongoClient("mongodb://localhost:27017/")
mydb = db["sample"]
mycln = mydb["details"]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)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)Update
# to update a single document
mycln.update_one({"name" : "foo"}, {"$set":{"age": 23}})Delete
# to delete a single document
doc1 = mycln.delete_one({"name" : "foo"})Python with Files
Create
Use open() function with c or a or w as mode.
file = open("myfile.txt","c")Read
Use open() function with r as mode.
file = open("myfile.txt","r")
print(file.read())Update or Append
Use open() function with a or w as mode.
file = open("myfile.txt","a")
file.write("Happy learning!!")
file.close()Delete
For deleting files, you must import os module and use os.remove() function.
import os
os.remove(filename)If you have quires and suggestions put them in the comments.Hope this Python Cheatsheet useful to you, Share & Help Other to learn 🙂
