Table of Contents |
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Basics
Comments
Comments start with a pound(#) sign.
Code Block |
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# define a number
time_elapsed_s = 12.34 |
Variables
Code Block |
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# define a number
time_elapsed_s = 12.34
#define a string
first_name = "John"
#define a boolean - True/False
is_online = True |
Input and Output
Code Block |
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first_name = input("What is your name? ")
print("Hello " + first_name) |
Type Conversions
Python has the following functions for type conversion:
- int(),
- float(),
- bool(),
- str()
Code Block |
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#Convert String to int
birth_year = input("What is your birth year: ")
age = 2021 - int(birth_year)
print(age)
# or another way
birth_year = int(input("What is your birth year: "))
age = 2021 - birth_year
print("Age: " - str(age)) |
Strings
When we define a string, it becomes an object of type string. We can call any methods of the object string.
Code Block |
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course = "Course Name"
index = course.find("u")
print(index)
#or to get True/False if an substring exists using IN
found = "Name" in course
print (found) |
Arithmetic Operators
Operator | Description | Example |
---|---|---|
+ | plus | 10 + 3 = 13 |
- | minus | 10 - 3 = 7 |
* | multiply | 10 * 3 = 30 |
/ | divide - returns float | 10 / 3 = 3.333 |
// | divide (whole number) | 10 // 3 = 3 |
% | modulus - remainder of division | 10 % 3 = 1 |
** | exponent | 10 ** 3 = 1000 |
+=, *=, ... | Augmented Assignment Operators | x+=3 = x=x+3 |
Comparison Operators
Operator | Description |
---|---|
> | Greater than |
>= | Greater than or equal |
< | Less than |
<= | Less than or equal |
== | Equal |
!= | Not Equal |
Logical Operators
Operator | Description | Example |
---|---|---|
and | logical and | price =20 print( price >10 and price < 30 ) |
or | logical or | price =20 print( price >10 or price < 30 ) |
not | price = 20 print (not price >10) |
If Statements
If statements use indentation instead of curly brackets in Java.
Code Block |
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temperature = 25
if temperature > 30:
print("It's a hot dat")
print("Drink plenty of water")
elif temperature > 25:
print("It's a nice day")
else:
print("It's a cold day")
print("Done") |
While Loops
While loops use indentation instead of curly brackets in Java.
Code Block |
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i=1
while i<=1_000:
print(i)
i=i+1 |
Notice in the above example we used an underscore to make reading the integer 1000 easier to read.
Lists
Lists are indexed starting at 0.
Code Block |
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names = ["Bob", "Sam", "John"]
print (names[0])
names [1] = "Samantha"
# to get second last element
print (names[-2])
# subset of list from 0 to 3 but excluding the end index 3.
# does not change original list
print (names[0:3]) |
List Methods include append, insert, etc..
Code Block |
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names = ["Bob", "Sam", "John"]
names.insert(1,"Barbara")
names.append("Tom")
print (names)
print ("Sam" in names)
print (len(names)) |
For Loops
Code Block |
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numbers = [1,2,3,4,5]
for item in numbers:
print(item) |
Range Function
A range function creates a list up to but not including the stop value supplied.
range(start, stop, step)
Parameter | Description |
---|---|
start | Optional. An integer number specifying at which position to start. Default is 0 |
stop | Required. An integer number specifying at which position to stop (not included). |
step | Optional. An integer number specifying the incrementation. Default is 1 |
Code Block |
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numbers = range(1,5)
for number in numbers:
print(number)
# Output:
1
2
3
4 |
Tuples
Tuples are just like lists but are immutable (can not be changed). Use round brackets to define a tupple.
Code Block |
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numbers = (1,2,3,4) |
Cheat Sheet
References
Reference | URL |
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Python for Beginners - Learn Python in 1 Hour | https://www.youtube.com/watch?v=kqtD5dpn9C8 |
Python Cheat sheet for hackers and developers | https://hakin9.org/python-cheat-sheet-for-hackers-and-developers/ |