pythonLearning

My first programs on Python

• module names should be lowercase with underscore (_) between words

5/12/2018

• to get input type

input("some input, please")

X - hours / Y - minutes ==> Find total minutes
X = int(input())
Y = int(input())
print(X*60 + Y)

9/12/2018

print(a, end = " ") # will print with space in the end
a,b = input().split() # if there is space or anything between a and b they will be sepaprated
a = int(a)
b = int(b)

10/12/2018

• for-cycle

for i in range(10):
for i in 2,3,5:

• range() function

range(start = 0, to, step = 1)

for i in range(n):
	print('*' * n)

• print() function

  print() #by default goes on the next line
  print(end = '') #will not go on the next line

• list comprehension

a, b =(int(i) for i in input().split())

• strings are not mutable

s = abcd
s[1] = e #will result in error

• print all characters in c

for c in genome:
	print(c)

• count all 'C' in genom

genome = input()
print(genome.count('C')) 

string functions

s.count(p) #returns how many times p is in s
s.lower()
s.upper()
s.find(p) #returns index of p in s (-1 if doesn't exist)
	if p in s: #check if here
s.replace(a, b) #replace a by b. original string will not change
#can use all together
s.upper().count('gt'.upper())

slicing

dna[1:-1:2]
dna[start: finish: step]
dna[::-1] #reverse

lists

• empty list

students = []

students = ['Dave', 'John', 'Rose', 'Jade']
for student in students:
	print('Hello ' + student + '!')
students[1] #John
students[::-1] #reverse list
len(students) #4

• lists can be added and mutiplied. Original lists don't change

fruit = [kiwi, apple, orange, pineapple]
newlist = students + fruits
newstudents = students * 4

• adding lists can be done in two ways

fruit.append('pear')
fruit += 'pear'

• inserting element at certain position

fruit.insert(1, 'plum')

• deleting element

students.remove('Jade') #will return string without 'Jade'
del students[0] #will remove 'Dave'

• look up for the element

students = ['Dave', 'John', 'Rose', 'Jade']
if 'Dave' in students:
	print("Dave is here")
if 'Dirk' not in students:
	print("Dirk is not here")
	
ind = students.index('Rose') #returns index
ind = students.index('Roxy') #error

• sorting list

ordered_students = sorted(students) #original list will not change
students.sort() #original list changed
students.min()
students.max()

• reversing list

students.reverse()
rev_students = reversed(students)
students[::-1]

• lists are mutable

a = [1, 2, 3]
b = a
a[1] = 4 #List object is shared 
# a = [1, 4, 3]
# b = [1, 4, 3]
b[2] = 5
# a = [1, 4, 5]
# b = [1, 4, 5]

• generating list

a = [0] * 5 #[0, 0, 0, 0, 0]
#list comprehension
a = [0 for i in range(5)] #[0, 0, 0, 0, 0]
a = [i*i for i in range(5)] #[0, 1, 4, 9, 16]
a = [int(i) for i in input().split()]

n = 3
a = [[0] * n] * n
a = [[0] * n for i in range(n)]
a = [[0 for j in range(n)] for i in range(n)]

12/12/2018

• functions

def name(arguments):
	#function body
	return

• function should be declared earlier than first used
• arbitrary number of arguments

def min(*a):
	m = a[0]
	for x in a:
		if m > x:
			m = x
	return m

• default arguments

def print(a = '', end = '\n'):
	#...

print() #will print empty string and go to next line

• when passing arguments without names they will be assigned in defined order

15/12/2018

• sets

s = set() #empty set
basket = {'apple', 'orange', 'plum', 'pear'}
'orange' in basket #True
'cherry' in basket #False
s.add(element)
s.remove(element) #if no element then ERROR
s.discard(element) #if no element then NO ERROR
s.clear()
len(s) #number of elements in set

• dictionary - key-value pairs
• creating dictionary

dict()
{}
d = {'a': 239, 10:100, 'key': 'value'}
print(d['a'])
print(d[10])

• operations with dictionaries

dictionary = {...}
key in dictioary #True/False
key not in dictionary #True/False
dictionary[key] = value #assigning
dictionary[key] #if key is not in dictionary then ERROR
dictionary.get(key) #returns value or None
del dictionary[key]

• dictionaries

1. are mutable
2. have no order
3. all keys are different
4. keys are immutable

• looking through the dictionary

d = {'C': 12, 'A': 23, 'T': 67, 'G': 18}
for key in d:
	print(key, end = ' ')
for key in d.keys():
	print(key, end = ' ')
for value in d.values():
	print(value, end = ' ')
for key,value in d.items():
	print(key, value, end = ';')

16/12/2018

• files
• reading from file

inf = open('file.txt', 'r') #open('file.txt')
s1 = inf.readline() #read first line
s2 = inf.readline() #read second line
inf.close()

with open('text.txt') as inf: #automaticly closing file
	s1 = inf.readline()
	s2 = inf.readline()

• file functions

s = inf.readline().strip() #taking away special characters
os.path.join('.','dirname','filename.txt')

• reading file line-by-line

with open('input.txt') as inf:
	for line in inf:
		line = line.strip()
		print(line)

• writing to the file

ouf = open('file.txt', 'w')
ouf.write('Some text\n')
ouf.write(str(25))
ouf.close()

with open('output.txt', 'w') as ouf:
	ouf.write('Some text\n')
	ouf.write(str(25))

• modules

import my_module
from my_module import foo
from my_module import *
from my_module import foo as my_foo

• requests

import requests

r = requests.get('https://example.com') #GET
print(r.text)

url = 'https://example.com'
par = {'key1': 'value1', 'key2': 'value2'}
r = requests.get(url, params = par) #passing parameters
print(r.url) #url GET 

url = 'http://httpbin.org/cookies'
cookies = {'cookies_are': 'working'}
r = requests.get(url, cookies = cookies) #sending request to the server
print(r.text)

print(r.cookies['example_cookie_name']) #using cookies from server