HowTo_Python.md

How to: python

• Lists
• Strings
• Tuples
• Packages
• Python version
• Kill all python processes
• Get time of process

---

Lists

• Add array to one single cell

  list.append(array)
  

• Add each element of an array to a separate cell of a list

  list.extend(array)
  

• Check if element is empty:

  for i in range (0, len(list)):
    if not list[i]:
        print (i)
  

• Delete element given index:

  array = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
  del array[1]
  -> 1
  

• Check if element is already in list:

  if element in list:
  

• Convert list of lists to one single list

  from itertools import chain
  long_list = list(chain.from_iterable(list_of_lists))
  

• Get unique elements (using sets)

  my_list_set = set(my_list)  
  unique_elements = list(my_list_set) # note that "list"  here is a function   
  

---

Strings

• Find substring in string:
  • In general (returns the index for the first letter):

    main_string = "ciao"
    sub_string = "ao"
    main_string.find(sub_string)
    

  • In if (returns -1 if string not found):

    if main_string.find(sub_string) != -1:
        print ("found")
    

    or

    if sub_string in main_string:
        print ("found")
    

• Find string in list of strings:
  • In if:

    if string in list_of_string:
        print ("found")
    

  • Get index:

    index = list_of_string.index(string)
    

• Find overlap between two list of strings (returns a list with overlapping terms):

  overlap = list(set(list_of_strings_1) & set(list_of_strings_2))
  

• Substitute sub_string in string:

  main_string = main_string.replace('old_sub_string', 'new_sub_string')  
  

• Split string:
  • In two parts, before and after character:

    part1, part2 = url.rsplit('/', 1)
    

  • Get only first or second part:

    part1 = url.rsplit('/', 1)[0]
    part2 = url.rsplit('/', 1)[1]
    

---

Tuples

• Find element in tuples and get index:

  if element in tuple:
        index = tuple.index(element)
  

• Check if tuple is empty:

  if len(tuple) == 0: 
     ...
  

---

Packages

• To install a package: pip install <packageName>
• To install a specific version of a package: pip install --force-reinstall <packageName>==1.2.0
• To upgrade a package: pip install <packageName> --upgrade
• To remove a package: pip uninstall <packageName>
• To list packages: pip freeze
• To see version of package: pip show <packageName>

---

Python version

• To know python version: python --version

---

Kill all python processes

• In terminal: pkill -f python

---

Get time of process

• To print out the time of a process:

  import time
  start_time = time.time()
  # [code here]
  print ("-> The total time was %.2f seconds (about %d min)" % ((time.time() - start_time), (time.time() - start_time)/60))