Python For Quantum Mechanics

Week 2: Cheatsheet

2.1 Flow Control

• If Statments

  • Documentation: https://docs.python.org/3/tutorial/controlflow.html

  if Condition==True:
      Execute this block
  elif Other_Condition==True:
      Execute this block
  elif Other_Condition==True:
      Execute this block
  .
  .
  .
  elif Other_Condition==True:
      Execute this block
  else:
      Execute this block
  

• Try and Except

  • Documentation: https://docs.python.org/3/tutorial/errors.html

  try:
      Block
  except:
      Block
  finally:
      Block
  

• While Loops

  • Documentation: https://docs.python.org/3/reference/compound_stmts.html#while

  While condition==True:
      Execute This Block
  

• Range and Zip

  • Documentation: https://docs.python.org/3/tutorial/controlflow.html#the-range-function

  range(start,stop,step)
  

  • Documentation: https://docs.python.org/3/library/functions.html#zip

  zip(a,b)
  

• For Loops

  • Documentation: https://docs.python.org/3/tutorial/controlflow.html#for-statements

  for i in (iterable object):
      Execute This Block
  

  enumerate(a)
  

• Break, Continue, Pass

  • Documentation: https://docs.python.org/3/tutorial/controlflow.html#break-and-continue-statements-and-else-clauses-on-loops

  break #stops loops action
  continue #moves to the next iteration in the loop
  pass #moves onto the rest of the code block and following iterations
  

2.2 Compact Code

• One-Line If and Else

  • Documentation: https://www.codegrepper.com/code-examples/python/python+single+line+for+loop+with+if+else

  x = one_thing if condtion else another_thing
  

• Comprehensions

  • Documentation: https://docs.python.org/3/tutorial/datastructures.html#list-comprehensions

  L = [x for x in (Iterable Object) if condition == True]
  

  • Documentation: https://docs.python.org/3/tutorial/datastructures.html#sets

  S = {x for x in (Iterable Object) if condition == True}
  

  • Documentation: https://docs.python.org/3/tutorial/datastructures.html#dictionaries

  D = {key:value for key,value in Dict.items() if condition == True}
  

• Generators

  • Documentation: https://docs.python.org/3/reference/expressions.html#generator-expressions

  G = (x for x in (Iterable Object) if condition == True)
  

2.3 External Data

• User Input

  • Documentation: https://docs.python.org/3/library/functions.html#input

  input('Prompt here: ')
  

• Reading from File

  • Documentation: https://docs.python.org/3/tutorial/inputoutput.html#reading-and-writing-files

  with open("file",'r') as f:
  
      f.read() #Reads entire file
      f.read(10) #Reads 10 characters
  
      f.readline() #Reads line
      f.readline() #Reads next line
  

• Writing to File

  • Documentation: https://docs.python.org/3/tutorial/inputoutput.html#reading-and-writing-files

  with open("file",'a') as f: # or 'w' 
      f.write("appends('a')/overwrites('w')")