Computer Science Computer Science 101101

If StatementIf Statement

Python Relational Operators Python Relational Operators Operator Meaning

< Less than> Greater than

== Equal<= Less than or equal>= Greater than or equal!= Not equal

Primitive ConditionsPrimitive Conditions ConditionsConditions are expressions which are expressions which

evaluate to evaluate to truetrue or or falsefalse..

One kind of condition is the One kind of condition is the comparison of two numerical values comparison of two numerical values of the same type.of the same type.

Examples:Examples: Payrate > 10Payrate > 10 (x+10) == (y*z -8)(x+10) == (y*z -8)

The If-StatementThe If-Statement The syntax for the If-Statement isThe syntax for the If-Statement is

if <condition> :if <condition> : <list of statements> <list of statements>

• <condition> would be replaced by actual <condition> would be replaced by actual condition, etc.condition, etc.

• The colon is requiredThe colon is required

• The list of statements, must be indented – The list of statements, must be indented – part of the syntax for Pythonpart of the syntax for Python

The If-StatementThe If-Statement

The semantics are as expected – The semantics are as expected –

• the condition is evaluatedthe condition is evaluated

• if the condition is true, the list of if the condition is true, the list of statements is executedstatements is executed

If-Statement SemanticsIf-Statement Semantics

T

F

Cond

If-Statement examplesIf-Statement examples if yearsWorked > 10 :if yearsWorked > 10 :

bonus = 1000 bonus = 1000

if age >= 65 :if age >= 65 : total = 0.85 * total total = 0.85 * total numSeniors = numSeniors + 1 numSeniors = numSeniors + 1

The If-else-StatementThe If-else-Statement The syntax for the If-Else-Statement isThe syntax for the If-Else-Statement is

if <condition> : if <condition> : <list of statements> <list of statements>

else : else : <list of statements> <list of statements>

Note colon after elseNote colon after else The semantics are as expected - The semantics are as expected -

• the condition is evaluatedthe condition is evaluated• if the condition is true, then the first list of if the condition is true, then the first list of

statements is executed; otherwise, the statements is executed; otherwise, the second list is executedsecond list is executed

If-Else-Statement examplesIf-Else-Statement examples if yearsWorked > 10 :if yearsWorked > 10 : bonus = 1000bonus = 1000

else : else : bonus = 500 bonus = 500

if age >= 65 :if age >= 65 : price = 0.85 * price price = 0.85 * price numSeniors = numSeniors + 1 numSeniors = numSeniors + 1 else : else : nonSeniors = nonSeniors + 1 nonSeniors = nonSeniors + 1

Python SessionPython Session

Python Session (cont)Python Session (cont)