virtual Environment : an environment which is same as the system interpreter but is isolated from the other python environments on the system.
Installation : to use virtual environment, we write
pip install virtualenv [install the package]
we create a new environment using :
virtualenv myenv [create new virtual env]
the next step after creating the virtual environment is to activate it. we can now use this virutal environment as a seperate python installation
PIP freeze command: PIP freeze returns all the packages installed in a given python environment along with the versions
"PIP freeze > requirement.txt"
the above command creates a file named requirements.txt in the same directory containing the output of PIP freeze
We can distribute this file to other users and they can recreate the same environment using :
PIP install -r requirements.txt
Lambda Functions : functions created using an expression using lambda keyword.
syntax : lambda arguments : expressions
expressions can be used as a normal functions.
square = lambda x : x*x
square(6) [returns 36]
sum = lambda a,b,c : a+b+c
sum(1,2,3) [returns 6]
bin method (strings) : creates a string from iterable objects
l = ["apple", "mango" ,"banana"]
",and,".join(l)
the above line will return "apple, and, mango, and, banana"
format method (strings) : formats the values inside the string into a desired output : template.format(p1,p2, ......) [ arguements]
syntax:
"{ } is a good { }".format("iam", "boy")
output : iam is agood boy
"{1} is a good {0}.format("iam", "boy")
output: boy is a good iam
Map, Filter and Reduce: Map applies a function to all the items in an input_list
syntax: map(function, input_list)
filter creates a list of items for which the function returns true
syntax: list(filter(function))
Reduce applies a rolling computation to sequential pair of elements
from functools import reduce
val = reduce (functin, ist1)
If the function computes sum of two numbers and the list is
[1, 2, 3, 4]
1 2 3 4 [Special Computation]
3 3 4
6 4
10
**function can be a lambda function
Programs :
1. #virtualenv
# For MacOS/linux users: source myprojectenv/bin/activate
# For windows powershell users: .\myprojectenv\Scripts\activate.ps1
# https://stackoverflow.com/questions/18713086/virtualenv-wont-activate-on-windows
import flask # flask - 0.5.2
import pandas as pd
import pygame
2. #lambda
# def func(a):
# return a+5
func = lambda a: a+5
square = lambda x: x*x
sum = lambda a, b, c: a+b+c
x = 3
print(func(x)) # Prints 8
print(square(x)) # Prints 9
print(sum(x, 1, 2)) # Prints 6
3. #join
l = ["Camera", "Laptop", "Phone", "ipad", "Hard Disk", "Nvidia Graphic 3080 card"]
# sentence = "~~".join(l)
# sentence = "==".join(l)
sentence = "\n".join(l)
print(sentence)
print(type(sentence))
4. #format
name = "cstechiie"
channel = "blog"
type = "Coding"
# a = f"This is {name}"
# a = "This is {}".format(name)
# a = "This is {} and his channel is {}".format(name, channel)
# a = "This is {0} and his {2} channel is {1}".format(name, channel, type)
a = "This is {} and his {} channel is {}".format(name, channel, type)
print(a)
5. #map
def square(num):
return num*num
l = [1, 2, 4]
# Method 1
l2 = []
for item in l:
l2.append(square(item))
print(l2)
# Method 2
print(list(map(square, l)))
6. #filter
# Filter Syntax: list(filter(function, list))
def greater_than_5(num):
if num > 5:
return True
else:
return False
g10 = lambda num: num>10
l = [1, 2, 3, 4, 5, 6, 7, 8, 89, 98]
print(list(filter(greater_than_5, l)))
print(list(filter(g10, l)))
7. #reduce
from functools import reduce
sum = lambda a, b: a+b
l = [1, 2, 3, 4]
val = reduce(sum, l)
print(val)
