#!/usr/bin/env python3
""" GENERAL """
#Python is case-sensitive !!!
#indentations instead of curly braces
#use 4 empty spaces OR tab
#do not mix tabs and spaces
#run python files from CommandPrompt or PowerShell:
#C:\>python filename.py arguments
type(a) #returns the type of a
sys.argv[0] #returns the name of the file
sys.argv[1] #returns the command line argument
print('things inside braces ',
'can be spread over multiple '+
'lines')
""" DOCUMENTING """
def myFunc(a):
"""This is a demo function
Arguments:
a: string entered by the user
Returns:
The same string appended by "bee"
"""
print(a+' + bee is')
return a + 'bee'
help(myFunc) #returns the description of the function
""" SCALAR TYPES """
#integer or float
6/3 #results float 2.0
6//3 #results integer 3
#convert to integer
int(3.5) #3
int(-3.5) #-3 (rounds toward zero)
int("300") #300
#None type
a = None
#Bool
bool(0) #false; only 0 is false, any other number is true
bool(0.0) #false
bool(1) #true
bool(-1.25) #true
bool([]) #false; any empty collection (string, list, etc..) is false
bool("") #false
bool([]) #true; any non-empty collection is true
bool([1,6]) #true
bool("0") #true
bool("False") #true
""" CONTITIONAL STATEMENTS """
if a < 5:
print("is smaller than five")
elif a < 3:
print("is smaller than 3")
else:
print("is equal or bigger than 5")
""" WHILE LOOP """
#will print 5,4,3,2,1
c = 5
while c != 0:
print (c)
c -= 1 #decrement by one
#will break the loop if
c = 5
while c != 0:
print (c)
if c == 3:
print("let's break here, no need to go down to 0")
break
c -= 1 #decrement by one
#will wait for the correct response :)
while True:
response = input("How many musketeers? ")
if response == "3" or response == "three":
print("That is correct !")
break
print("Wrong answer.")
""" STRING """
#using escape characters
path = "c:\\\\Users\d\'Artagnan"
print(path)
#using raw string instead
path = r"c:\\Users\d'Artagnan"
print(path)
#encode and decode strings with special characters
francais = "réponse"
data = francais.encode("utf-8")
print(data)
french = data.decode("utf-8")
print(french)
#string and parts of a string
a = 'montreal'
print(a[0]) #m
print(a[1]) #o
print(a[-1]) #l
print(a[0:5]) #montr
print(a[2:5]) #ntr
print(a[2:-2]) #ntre
print(a[:]) #montreal
#join and split
colors = '-'.join(['red','green','blue'])
print(colors) #red-green-blue
print(colors.split('-')) #['red', 'green', 'blue']
#concatenate with join or with +
print(''.join(['uga','buga'])) #ugabuga
print('uga'+'buga') #ugabuga
#partition
left, middle, right = 'Jack and Jill'.partition(' and ')
print(left) #Jack
print(middle) # and
print(right) #Jill
#more methods
print('hello'.capitalize()) #Hello
print('hello'.replace('e','a')) #Hallo
print('hello'.isalpha()) #True
print('hello'.isdigit()) #False
print(len('green')) #5
#format method
a = "Jack"
b = "Jill"
print('Hello, {0} and {1} !'.format(a,'Jimmy')) #Hello, Jack and Jimmy !
print(f'Hello, {a} and {b} !') #Hello, Jack and Jill !
#another format exemple
a=3.14159
print(f'pi = {a} ') #3.14159
print(f'pi = {a:.2f} ') #3.14
""" RANGE """
print(list(range(10))) #[0, 1, 2, 3, 4, 5, 6, 7, 8, 9
print(list(range(5,10))) #[5, 6, 7, 8, 9]
print(list(range(0,10,2))) #[0, 2, 4, 6, 8]
for i in range (10): # will output 0,1,2,3,4,5,6,7,8,9
print(i)
for i in range (5,10): # will output 5,6,7,8,9
print(i)
for i in range (0,10,2): # will output 0,2,4,6,8
print(i)
""" LIST """
a = [] #declare empry list
a.append('X') #add values in a list
print(a) #['X']
b = [1,33,66] #declare list with values
b[0] = 'F' #modify value
print(b) #['F', 33, 66]
mylist = "m o n t r e a l".split()
print(mylist) #['m', 'o', 'n', 't', 'r', 'e', 'a', 'l']
print(mylist[0]) #m
print(mylist[1]) #o
print(mylist[-1]) #l
print(mylist[0:5]) #['m', 'o', 'n', 't', 'r']
print(mylist[2:5]) #['n', 't', 'r']
print(mylist[2:-2]) #['n', 't', 'r', 'e']
print(mylist[:]) #['m', 'o', 'n', 't', 'r', 'e', 'a', 'l']
#copying lists - creates shallow copies
seq = [1,2,3]
seq2 = seq[:] #creates shallow copy
seq3 = seq.copy() #creates shallow copy
seq4 = list(seq) #creates shallow copy
seq5 = seq #creates a reference !!!
seq[0] = 100 #modifying original list
print(seq) #[100, 2, 3]
print(seq2) #[1, 2, 3]
print(seq3) #[1, 2, 3]
print(seq4) #[1, 2, 3]
print(seq5) #[100, 2, 3]
#find value in a list, count value instances
mylist = ['heads','shoulders','knees','and','toes','knees','and','toes']
i = mylist.index('heads')
print(i) #0
print(mylist[i]) #heads
print('knees' in mylist) #True; 'in' and 'not in' are supported
print(mylist.count('knees')) #2
#remove elements by index or by value
mylist = ['heads','shoulders','knees','and','toes']
del mylist[0]
print(mylist) #['shoulders', 'knees', 'and', 'toes']
mylist.remove('shoulders')
print(mylist) #['knees', 'and', 'toes']
mylist.insert(0,'head')
print(mylist) #['head', 'knees', 'and', 'toes']
#convert string to a list
mylist = ['heads','shoulders','knees','and','toes']
str = ' '.join(mylist)
print(str) #heads shoulders knees and toes
#growing lists
m = [1,2,3]
k = m + [4]
k += [5]
k.extend([6,7])
print(k) #[1, 2, 3, 4, 5, 6, 7]
#sort and inverse
m = [4,2,1,3]
m.sort()
print(m) #[1, 2, 3, 4]
m.reverse() #same as m.sort(reverse=True)
print(m) #[4, 3, 2, 1]
#sort by length
m = ['Melbourn','Oz','Paris']
m.sort(key=len)
print(m) #['Oz', 'Paris', 'Melbourn']
m = ['Melbourn','Oz','Paris']
m.sort(key=len,reverse=True)
print(m) #['Melbourn', 'Paris', 'Oz']
""" DICTIONNARY """
#can be multi-line, thanks to the {}
d = { 'Yahoo': 'http://yahoo.com',
'Google': 'http://google.com'}
d['Google'] = 'www.google.com' #modify the value of 'Google'
d['Redmine'] = 'www.redmine.com' #add new values
print(d) #{'Yahoo': 'http://yahoo.com', 'Google': 'www.google.com', 'Redmine': 'www.redmine.com'}
#keys must be immutable
#values can be mutable
#order is arbitrary !!!!
#copy dictionnaries
e = d.copy()
f = dict(d)
#update from another dictionnary
f = {'red':'rouge', 'green':'verde'}
g = {'yellow':'jaune', 'green':'vert'}
f.update(g) #add and update (f to g)
print(f) #{'red': 'rouge', 'green': 'vert', 'yellow': 'jaune'}
#list keys and values
colors = {'red': '#ff0000', 'blue': '#0000ff'}
for key,value in colors.items():
print(key + ' is ' + value)
#verify membership and remove items
colors = {'red': '#ff0000', 'blue': '#0000ff'}
print('red' in colors #True; 'in' and 'not in' are supported
del colors['red']
print('red' in colors) #True
""" SET """
e = set() #creates an empty set
s = {1,2,'a','b'} #creates set with values
print(s) #{1, 2, 'b', 'a'}
#use set() to remove duplocates from a list
t = [1,2,2,3,3,3,4,4,5,5,5,5]
s = set(t)
print(s) #{1, 2, 3, 4, 5}
#in and not in are supported
#add(element) to add elements; existing elements are ignored
#remove(element) to remove elements (error if the element )
#discard(element) to remove elements
#update() to update elements
#copy sets
d = {1,2,'a','b'}
e = d.copy()
f = set(d)
#used to compute unions, intersections, differences, subsets
""" FOR LOOP """
#with range
for i in range (10): # will output 0,1,2,3,4,5,6,7,8,9
print(i)
#with list
cities = ['London', 'Paris', 'Oslo']
for a in cities:
print(a)
#with dictionnary
colors = {'red': '#ff0000', 'blue': '#0000ff'}
for a in colors:
print(a) #will return the key
for a in colors:
print(colors[a]) #will return the value
#break and continue
for i in range (5): # will stop and only output 0,1,2
if i == 3:
break
print(i)
for i in range (5): # will skip 3 and output 0,1,2,4
if i == 3:
continue
print(i)
""" FUNCTION """
def myFunc(a):
print(a+' + bee is')
return a + 'bee'
a = input('Type something : ')
print(myFunc(a)) #using the result returned by the function
""" FUNCTION ARGUMENTS """
def f(a,b="bananas"): #b argument has a default value
print(a + ' and ' + b)
f('apples') #apples and bananas
f('apples', 'strawberries') #apples and strawberries
f(b="dogs", a="cats") #cats and dogs
#passing additional arguments
def function (argument, *args) # *args is a list
def function (argument, **kwargs) # **kwargs is a dictionnary
""" ARGUMENT PASSING """
#k and m are the same thing
m = [1,2]
def modify(k):
k.append(3)
print('k value is ' + str(k)) #k value is [1, 2, 3]
print('k id is ' + str(id(k))) #k id is 58376960
modify(m)
print('m value is '+str(m)) #m value is [1, 2, 3]
print('m id is ' + str(id(m))) #m id is 58376960
#k and m are no loger the same thing
m = [1,2]
def modify(k):
k = [1,2] #here is when k gets redirected to another object in the memory
k.append(3)
print('k value is ' + str(k)) #k value is [1, 2, 3]
print('k id is ' + str(id(k)) #k id is 49463088
modify(m)
print('m value is '+str(m)) #m value is [1, 2]
print('m id is ' + str(id(m))) #m id is 49595136
""" VARIABLE SCOPING """
#access variable within a function
count = 6
laps = 6
def increase(a,b):
count = a
count += 1 #count becomes local variable
global laps #gives access to the global variable
laps = b
laps += 1 #modifies the global variable
increase(count,laps)
print(count) #6
print(laps) #7
""" EXCEPTION HANDLING """
try:
x = int('sdf')
print('Conversion succeeded! x = ', x)
except ValueError: #error message for a specific error
print('Value error')
except IndentationError: #error message for another error
pass #do nothing
except (TypeError, NameError): #regroup errors
print('Conversion failed')
except Exception: #will catch any error
print('Unknown error')
#get error details
try:
x = int('sdf')
except Exception as error:
print('Unknown error - ', error )
""" CLASS """
class Student():
shcool = 'Ahuntsic' #class attribute - the same for every instance
def __init__(self, name): #'self' refers to the instance;
print (name + ' created')
self._name = name #creating instance attribute
def __str__(self):
return 'Student ' + self._name #will be returned when the instance is printed
def name_format(self): #functions inside classes = methods
return self._name.capitalize() #calitalizes the instance attribute 'name'
mark = Student('mark') #'mark' is an instance of the class 'Student'
john = Student('john') #another instance of the class 'Student'
print(mark.name_format()) #Mark
print(john.name_format()) #John
print(mark) #Student mark
print(john) #Student john
print(Student.shcool) #Ahuntsic
print(mark.shcool) #Ahuntsic
print(john.shcool) #Ahuntsic
class HighSchoolStudent(Student): #HighSchoolStudent class is derived from Student class
shcool = 'ETS' #overwrites the parent class attribute
def name_format(self): #overwrites the parent method
a = super().name_format() #the parent method is still accessible via super()
return ' '.join(a) #adds spaces
maria = HighSchoolStudent('maria') #maria created
print(maria.shcool) #ETS
print(maria.name_format()) #M a r i a
""" IMPORT """
# --- tools.py ---- #a simple exemple of python module
def format_names(a):
return a.capitalize()
#------------------
# --- main.py ----
import tools #import tools.py; note that .py is omitted
print( format_names('maria')) #rises an error
print(tools.format_names('maria')) #works fine
#------------------
# --- main.py ----
from tools import * #import all from tools.py
print( format_names('maria')) #works fine
print(tools.format_names('maria')) #rises an error
#------------------
# --- main.py ----
from tools import format_names #import specific function from tools.py
print( format_names('maria')) #works fine
print(tools.format_names('maria')) #rises an error
#------------------
# --- main.py ----
from tools import format_names as fnam #import with an alias
print( format_names('maria')) #rises an error
print(fnam('maria')) #works fine
#------------------
#Module code is executed once, on first import
#this helps tell if the file is imported or executed directly
if __name__ == '__main__':
print('the file is executed alone')
else:
print('the file is imported')
#Some definitions :
#Python module - convenient import
#Python script - convenient execution from command line
#Python program - perhaps composed of many modules
"""
WORKING WITH FILES """
#write
f = open('test.txt', mode='at', encoding='utf-8') #'at' is append text
f.write('just testing ')
f.write('new things\n') #both 'write'
and 'writelines' require \n to end a line
f.writelines(['more tests',
' comming soon\n',
'farewell ',
'my friend'])
f.close()
#readline
g = open('test.txt', mode='rt', encoding='utf-8') #'rt' is read text
print(g.readline()) #will read the
first line
print(g.readline()) #will read the
next line
g.close()
g = open('test.txt', mode='rt', encoding='utf-8')
list = g.readlines() #will read all
lines into a list
g.close()
print(list)
#filename passed
as argument and reads all the lines from a file
import sys
def main(filename):
f = open(filename, mode='rt', encoding='utf-8')
for line in f:
print(line)
f.close()
main(sys.argv[1])
""" EXECUTABLE FILE """
#to install the exe generator, type in PowerShell :
#>pip install pyinstaller
#to create an exe from somefile.py :
#>pyinstaller --onefile somefile.py
