The Python Language: Basics
Numbers, Arithmetics
Two types of numbers exist,
- int
- float, 15 digits, other digits are float error
It is worth noting that in Python 2, we have
print(1.0/3)
# will give us float numbers
# 0.333333333333
while
print(1/3)
# will only give us int
# 0
However, this was changed in Python 3.
Variables, Functions, Conditions
A variable name should start with either a letter or an underscore.
Variables defined inside a function is local and there is no way to find it or use it outside the function. It is even possible to reuse an already used global variable inside a function.
# num1 is a global variable
num1 = 1
print(num1)
# num2 is a local variable
def fun():
num1 = 2
num2 = num1 + 1
print(num2)
fun()
where the first line will give us 1 but the second output is 3. (Code from Coursera course interactivepython-005/lecture/15.)
If we want to use the global variable and change the value of it, the program can be like this,
num = 4
def fun1():
global num
num = 5
def fun2():
global num
num = 6
# note that num changes after each call with no obvious explanation
print(num)
fun1()
print(num)
fun2()
print(num)
from Coursera course interactivepython-005/lecture/15.
Start a function by a comment says what the function does.
def triangle_area(base, height): # header - ends in colon
area = (1.0 / 2) * base * height # body - all of body is indented
return area # body - return outputs value
from Coursera course interactivepython-005/lecture/8.
: indicates that a block code is following, which should be indented.
# will return True if a year is a leap year on Mars
def is_leap_year(year):
if year % 3000 == 0:
return False
elif year % 1000 == 0:
return True
elif year % 100 == 0:
return False
elif (year % 2 == 0) and (year % 10 == 0):
return True
else:
return False
Zen Code
Filter, Map, and List Comprehension
filter(), map(), reduce(), and list comprehension: link to code <https://repl.it/@emptymalei/Python-filter-map-reduce>_
Super function
In python you can access parent class properties easily.
class MyParentClass(object):
def __init__(self):
pass
class SubClass(MyParentClass):
def __init__(self):
MyParentClass.__init__(self)
To access the sub class properties, we can use super function.
class MyParentClass():
def __init__(self):
pass
class SubClass(MyParentClass):
def __init__(self):
super()
wiki/programming-languages/python/basics:wiki/programming-languages/python/basics Links to:L Ma (2018). 'The Python Language: Basics', Datumorphism, 03 April. Available at: https://datumorphism.leima.is/wiki/programming-languages/python/basics/.