Python is an interpreted, high-level and general-purpose, dynamically typed programming language
Python is also Object oriented, modular oriented and a scripting language.
In Python, everything is considered as an Object.
A python file has an extension of .py
Python follows Indentation to separate code blocks instead of flower brackets({}).
We can run a python file by the following command in cmd(Windows) or shell(mac/linux).
$ python <filename.py>
or $ python3 <filename.py>
By default, python doesn’t require any imports to run a python file.
nano/cat > nameProgram.py
python nameProgram.py
Data Type | Description |
---|---|
int | Integer values [0, 1, -2, 3] |
float | Floating point values [0.1, 4.532, -5.092] |
char | Characters [a, b, @, !, `] |
str | Strings [abc, AbC, A@B, sd!, `asa] |
bool | Boolean Values [True, False] |
complex | Complex numbers [2+3j, 4-1j] |
Keyword | Description | Category |
---|---|---|
True | Boolean value for not False or 1 | Value Keyword |
False | Boolean Value for not True or 0 | Value Keyword |
None | No Value | Value keyword |
and | returns true if both (oprand) are true (other language && ) | Operator keyword |
or | returns true of either operands is true (other language) | Operator keyword |
in | returns true if word is in iterator | Operator keyword |
is | returns true if id of variables are same | Operator keyword |
not | returns opposite Boolean value | Operator Keyword |
if | get into block if expression is true | conditional |
elif | for more than 1 if checks | conditional |
else | this block will be executed if condition is false | conditional |
for | used for looping | iteration |
while | used for looping | iteration |
break | get out of loop | iteration |
continue | skip for specific condition | iteration |
def | make user defined function | structure |
class | make user defined classes | structure |
lambda | make anonymous function | structure |
with | execute code within context manager’s scope | structure |
as | alias for something | structure |
pass | used for making empty structures(declaration) | structure |
return | get value(s) from function, get out of function | returning keyword |
yield | yields values instead of returning (are called generators) | returning keyword |
import | import libraries/modules/packages | import |
from | import specific function/classes from modules/packages | import |
try | this block will be tried to get executed | exception handling |
except | is any exception/error has occured it’ll be executed | exception handling |
finally | It’ll be executed no matter exception occurs or not | exception handling |
raise | throws any specific error/exception | exception handling |
assert | throws an AssertionError if condition is false | exception handling |
async | used to define asynchronous functions/co-routines | asynchronous programming |
await | used to specify a point when control is taken back | asynchronous programming |
del | deletes/unsets any user defined data | variable handling |
global | used to access variables defined outside of function | variable handling |
nonlocal | modify variables from different scopes | variable handling |
Operator | Description | |
---|---|---|
( ) | grouping parenthesis, function call, tuple declaration | |
[ ] | array indexing, also declaring lists etc. | |
! | relational not, complement, ! a yields true or false | |
~ | bitwise not, ones complement, ~a | |
- | unary minus, - a | |
+ | unary plus, + a | |
* | multiply, a * b | |
/ | divide, a / b | |
% | modulo, a % b | |
+ | add, a + b | |
- | subtract, a - b | |
« | shift left, left operand is shifted left by right operand bits (multiply by 2) | |
>> | shift right, left operand is shifted right by right operand bits (divide by 2) | |
< | less than, result is true or false, a %lt; b | |
<= | less than or equal, result is true or false, a <= b | |
> | greater than, result is true or false, a > b | |
>= | greater than or equal, result is true or false, a >= b | |
== | equal, result is true or false, a == b | |
!= | not equal, result is true or false, a != b | |
& | bitwise and, a & b | |
^ | bitwise exclusive or XOR, a ^ b | |
| | bitwise or, a | b |
&&, and | relational and, result is true or false, a < b && c >= d | |
||, or | relational or, result is true or false, a < b || c >= d | |
= | store or assignment | |
+= | add and store | |
-= | subtract and store | |
*= | multiply and store | |
/= | divide and store | |
%= | modulo and store | |
«= | shift left and store | |
>>= | shift right and store | |
&= | bitwise and and store | |
^= | bitwise exclusive or and store | |
|= | bitwise or and store | |
, | separator as in ( y=x,z=++x ) |
List is a collection which is ordered and changeable. Allows duplicate members.
Lists are created using square brackets:
thislist = ["apple", "banana", "cherry"]
List items are ordered, changeable, and allow duplicate values.
List items are indexed, the first item has index [0]
, the second item has index [1]
etc.
The list is changeable, meaning that we can change, add, and remove items in a list after it has been created.
To determine how many items a list has, use the len()
function.
list1 = ["abc", 34, True, 40, "male"]
thislist = list(("apple", "banana", "cherry")) # note the double round-brackets
pop() function removes the last value in the given list by default.
thislist = ["apple", "banana", "cherry"]
print(thislist.pop()) # cherry
print(thislist.pop(0)) #apple
thistuple = ("apple", "banana", "cherry")
[0]
, the second item has index [1]
etc.When we say that tuples are ordered, it means that the items have a defined order, and that order will not change.
thistuple = ("apple", "banana", "cherry", "apple", "cherry")
len()
function:thistuple = ("apple", "banana", "cherry")
print(len(thistuple))
thistuple = ("apple",)
print(type(thistuple))
# NOT a tuple
thistuple = ("apple")
print(type(thistuple))
thistuple = tuple(("apple", "banana", "cherry")) # note the double round-brackets
print(thistuple)
thisset = {"apple", "banana", "cherry"}
Unordered means that the items in a set do not have a defined order.
Set items can appear in a different order every time you use them, and cannot be referred to by index or key.
len()
method.thisset = {"apple", "banana", "cherry"}
print(len(thisset))
set1 = {"apple", "banana", "cherry"}
set2 = {1, 5, 7, 9, 3}
set3 = {True, False, False}
set4 = {"abc", 34, True, 40, "male"}
set()
constructor to make a set.thisset = set(("apple", "banana", "cherry")) # note the double round-brackets
set1 = {"apple", "banana", "cherry"}
frzset=frozenset(set1)
print(frzset)
thisdict = {
"brand": "Ford",
"model": "Mustang",
"year": 1964
}
thisdict = {
"brand": "Ford",
"model": "Mustang",
"year": 1964
}
print(thisdict["brand"])
len()
function.print(len(thisdict))
thisdict = {
"brand": "Ford",
"electric": False,
"year": 1964,
"colors": ["red", "white", "blue"]
}
car = {
"brand": "Ford",
"model": "Mustang",
"year": 1964
}
x = car.pop("model")
print(x)# Mustang
print(car)#{'brand': 'Ford', 'year': 1964}
if condition:
pass
elif condition2:
pass
else:
pass
Python has two primitive loop commands:
while
loop we can execute a set of statements as long as a condition is true.i = 1
while i < 6:
print(i)
i += 1
break
statement we can stop the loop even if the while condition is trueWith the continue statement we can stop the current iteration, and continue with the next.
A for loop is used for iterating over a sequence (that is either a list, a tuple, a dictionary, a set, or a string).
This is less like the for keyword in other programming languages, and works more like an iterator method as found in other object-orientated programming languages.
With the for loop we can execute a set of statements, once for each item in a list, tuple, set etc.
fruits = ["apple", "banana", "cherry"]
for x in fruits:
print(x)
The else keyword in a for loop specifies a block of code to be executed when the loop is finished. A nested loop is a loop inside a loop.
adj = ["red", "big", "tasty"]
fruits = ["apple", "banana", "cherry"]
for x in adj:
for y in fruits:
print(x, y)
for x in [0, 1, 2]:
pass
def function_name():
return
function_name()
None
Reference: Awesome Cheet Sheets by LeCoup