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  • Variable names can contain only letters, numbers, and underscores.
  • Variables can start with a letter or an underscor, but not wih a number
  • Spaces are not allowed in variable names, but underscores can be used to separate words
  • Variable names should be short but descriptive
  • Be careful when using lowercase letter l and the uppercase letter 0, as they can be confused with the numbers 1 and 0.

Strings

String - is a series of characters. Anything inside quotes is considered a string in Python, and you can use single or double quotes around your strings like this: "This is a string." 'This is also a string.'

-String Methods: method title() - changes each word to title case, where each word begins with a capital letter.

F-Strings

first_name = "ada"
last_name = "lovelace"
full_name = f"{first_name} {last_name}"
# strings like these are called f-strings. f stands for format. we use them to inser variables into a string
print(full_name)

To add tab use \t Example:

print("\tPython")

To add a newline in a string, use the character combination \n:

print("Languages:\nPython\nC\nJavaScript")

*You can also combine \n\t"

print("Languages:\n\tPython\n\tC\n\tJavaScript")

Stripping Whitespace

Use rstrip() method to remove whitespaces - FROM THE RIGHT SIDE

favorite_language = 'python '
favorite_language.rstrip()

Use lstrip() method to remove whitespaces - FROM THE RIGHT SIDE

favorite_language = 'python '
favorite_language.lstrip()

Use strip() method to remove ALL WHITE SPACES!

favorite_language = 'python '
favorite_language.strip()

Avoiding Syntax Errors with Strings

-Use double quotes to avoid apostrophe related errors.

#apostrophe.py 
# Avoiding Syntax Errors with Strings
message = "One of Python's strenths is its diverse community."
#doublequotes to apustrophe
print(message)

NUMBERS IN PYTHON

INTEGERS

You can use + , - , * , / with integers to add, subtract, multiply, and divide

2 + 3
3 - 2
2 * 3
3 / 2

Python uses two multiplication symbols to represent exponents

3 ** 2
3 ** 3
10 * 6

Python also supports the order of operations too:

>- For example:
>  2 + 3 * 4 # will result to 14
>  (2 + 3) * 4 # will result in 20, as brackets take precedence

FLOAT NUMBERS

0.1 + 0.1
0.2 + 0.2
# and etc.

INTEGERS AND FLOATS

input: 4/2 # when you divide any two numbers, even if they are integers that result in a whole number, you'll always get a float value! output: 2.0

_If you mix an integer and a float in any other operation, you'll get a float as well:

1 + 2.0 # result: 3.0
2 * 3.0 # result: 6.0

Python defaults to a float in any operation that uses a float, even if the output is a whole number

Underscores in Numbers

When you are writing numbers, you can group digits using underscores to make large numbers more readable

universe_age = 14_000_000_000
print(universe_age)
14000000000

Python ignores underscores for both float and int values

MULTIPLE ASSIGNMENT

You can assign values to more than one variable using a single line of code in Python:

x, y, z = 0, 0, 0

CONSTANTS

Constant - is a variable whose value stays the same throughout the life of a program. Python doesn't have built-in constant types, but Python programmers use all capital letters to indicate a variable shouls be treated as a constant and never be changed.

MAX_CONNECTIONS = 5000

COMMENTS

# - indicates a comment

''' this is a 
multiline comment '''

ZEN OF PYTHON

Experienced Python programmers will encourage you to avoid complexity and aim for simplicity whenever possible. The Python community's philosophy is contained in "The Zen of Python" by Tim Peters. To read the brief set of principles use:

import this

Beautiful is better than ugly.

Explicit is better than implicit.

Simple is better than complex.

Complex is better than complicated.

Flat is better than nested.

Sparse is better than dense.

Readability counts.

Special cases aren't special enough to break the rules.

Although practicality beats purity.

Errors should never pass silently.

Unless explicitly silenced.

In the face of ambiguity, refuse the temptation to guess.

There should be one-- and preferably only one --obvious way to do it.

Although that way may not be obvious at first unless you're Dutch.

Now is better than never.

Although never is often better than right now. If the implementation is hard to explain, it's a bad idea.

If the implementation is easy to explain, it may be a good idea.

Namespaces are one honking great idea -- let's do more of those!