my_python_essentials.md

My Python Essentials

The following python snippets are used frequently

Coding

• String formatting

age = 45
name = "abhijit"
# print("Hello {0}, your age is {1}".format(name, age))
print(f"Hello {name}, your age is {age}")     # since python v3.6

• Function definition

def print_a_message():
    print("abhijit")

my_function = print_a_message 	# assigning a function with another function

my_function()		# Run this function

• Function defined within another function

  Correct:

def my_function():
	my_other_function()

def my_other_function():
	print("Hello world")

# this works fine, because 'my_other_function' is defined yet.
my_function()

Wrong:

def my_function():
	my_other_function()

# this gives error, because 'my_other_function' is not defined yet.
my_function()

def my_other_function():
	print("Hello world")

• Function assignment

def func_a():
	print("Function a")

func_a()
"""
  NOTE: b is a variable & it has been assigned with a function
"""
b = func_a
b()

• Convert a list of string into float or int

>>> x = ["545.0", "545.6", "999.2"]
>>> map(float, x)
[545.0, 545.60000000000002, 999.20000000000005]
>>>

• dictionary

>>> dict(name="abhijit", age=26)
{'name': 'abhijit', 'age': 26}

• binary representaion

>>> print("{0:b}".format(45))
101101

• reversed iterator

for i in reversed(range(8)):
    print(i)

• truncate string

some_var = 'AAAH8192375948'
print(some_var[:5]) # AAAH8		starting 5 characters
print(some_var[:-5]) # AAAH81923	upto (-4th) character from start
print(some_var[-5:]) # 75948		from (-5th) character to end

• Check version of package

import pandas
print(pandas.__version__)

• remove duplicate strings from a list

a = ['DICD_AA_Dns_Line_Mean', 'DICD_AA_Dns_Line_Mean', 'DICD_AA_Dns_Line_Mean', 'DICD_AA_Iso_Line_Mean', 'DICD_AA_Iso_Line_Mean', 'DICD_AA_Iso_Line_Mean']
print(a)
a = list(set(a))
print(a)		# returns ['DICD_AA_Iso_Line_Mean', 'DICD_AA_Dns_Line_Mean']

Code Optimization

• Lambda

'''
# M-1
def compute_x(y):
    return 5*y + 2

print(compute_x(3))

# M-2
y = lambda x : 5*x+2
print(y(3))

More

• Map

items = [1, 2, 3, 4, 5]

# M-1
squared = []
for i in items:
    squared.append(i**2)
print(squared)

# M-2
squared2 = list(map(lambda x: x**2, items))
print(squared2)

More

• Filter

lst = ['a', 'ab', 'abc', 'bac']

# M-1
res = [k for k in lst if 'ab' in k]
print(res)	# ['ab', 'abc']

# M-2
res = filter(lambda k: 'ab' in k, lst)
print(res)	# ['ab', 'abc']

More