1b: Basic syntax and data types

1. The editor pane (for "script mode", TP11)
2. The variable explorer
3. The console (for "interactive mode", TP11)

Do you know where you are saving your script-name.py?

We recommend:

./PYW/1a ./PYW/1b ./PYW/1b/sphere.py

Etc.

One of the basic units of data, like a number or string, that a program manipulates.

5
"hi"
True

A name that refers to a value (or a memory location labelled with a name, and to which a value has been asigned).

var1 = 5

message = "hi"

A combination of variables, operators, and values that represents a single result.

(2 + 2)

A section of code that represents a command or action. So far, the statements we have seen are assignments and print statements.

a = 3

The categories to which values belong to. In Python, we have four primitive Data Types:

• Integer
• Float
• String
• Boolean

a = 100
b = 100.0
c = "messag"
d = True
e = False

A special symbol that represents a simple computation like addition, multiplication, or string concatenation.

• - * / // % **

The operator // is called the "floor division" operator in Python. It performs division and then rounds down to the nearest whole number.

It's closely related to the modulo operator %, which shows the remainder of a division of two numbers.

print(8 // 3)
print(16 % 3)

print(2 ** 3)

Information in a program that is meant for other programmers (or anyone reading the source code) and has no effect on the execution of the program.

variable a will be used later on, in an if-statement
a = True

“Syntax” refers to the structure of a program and the rules about that struc- ture. For example, parentheses have to come in matching pairs, so (1 + 2) is legal, but 8) is a syntax error.

(2+2)

The second type of error is a runtime error, so called because the error does not appear until after the program has started running.

Examples:

• ZeroDivisionError
  • When a number is divided by zero.
• NameError
  • When a name is used to which no value has yet been assigned
• TypeError
  • When an operation is performed with incompatible types.

numerator = 10
denominator = 0

result = numerator / denominator
print(result)

a = 2

print(a+b)

a = 2
b = "test"

print(a+b)

• PEMDAS
  1. Parentheses
  2. Exponentiation
  3. Multiply & divide
  4. Adding & subtracting

print((1 + 2) * 2)

When in doubt, use parentheses.

Also, have a look at this:

a = 5e5 # e5 = *10**5

print(a)

print(a/2)

There are some special characters!

\n    new line
\t    tab
\"    double quotation mark
\'    single quotation mark
\\    backslash

print("hi all \\how are you doing?")

Concatenation

print("pigs" + " " + "cows")

Repetition

print("pigs " * 10)

Boolean operators produce booleans. They work with boolean values, for example …

== means "is equal to"

print(True == False)
print(True == True)

… but can also work with other data types:

print(1 == 2)
print("hi" == "hi")

<= means bigger/smaller than, or equal to

print(2 <= 2)

!= means "not equal to"

print(2 != 3)

You can also combine things:

print(4 > 3 < 5)

print(<item1>, <item2>, . . . <itemx>, sep=' ', end='\n')

• Items separated from each other with ","
• sep = separator character (space by default)
• end = termination of character (new line by default)

#text = "this"+"is"+"a"+"test"

print("this","is","a","test", sep='-', end='')

variable_name = input("here you write a sentence to be displayed to the user")

(Reminder to self: show in Spyder or console).

age = input("Please enter your age: ")

Note that the output is a string.

You can convert a string to other data types:

a = "30"
a = int(a)
print(a+1)

And you can convert an integer or a float to a string:

a = 30
a = str(a)
print(a+"hi")