Python Help Sheet

Basic Python

Basic Operators

Arithmetic Operators

• + Addition
• - Subtraction
• * Multiplication
• / Division

Others

• Use round brackets () to specify order of operations.
• You may add spaces before and after operators to make expressions more readable, e.g. (1 + 2) * 5 is the same as (1+2)*5.
• Anything that comes after the # is considered a comment and is ignored by IDLE.

Strings

• Strings are enclosed by quote marks ''.
• + joins two strings, e.g. 'python' + ' ' + 'cool' evaluates to 'python cool'.
• * repeats a string, e.g. 'gee' * 3 gives 'geegeegee'
• You can mix and match them, e.g. 'b'+'a'*5 gives 'baaaaa'

Data Types

You should recognize different data types in python, which are treated differently by IDLE.

• Numbers
• Strings
• True/False values

Example of True/False values

• 5 < 5 gives the boolean False
• 5 == 5 gives the boolean True

Variable

You can use variables to ask Python to remember values by using the = operator. You can also use = to update the value of existing variables. For example,

greeting = 'howdy'  # greeting is assigned a value
new_greeting = greeting * 4  # IDLE recalls the stored value here
print(new_greeting)  # this will print 'howdyhowdyhowdyhowdy'
new_greeting = greeting + ' do?'  # the variable new_greeting is updated
print(new_greeting)  # this will print 'howdy do?'

Do not use variable names that start with a number.