12th. If branch statement expression constructs

1, conditional judgment: Boolean expression: 0 or 1, not 0 is considered to be true

2, relational expression: >,<,==,!=,>+,<=

3, logical expression: and Or not

4,in,not in

True, False is a python built-in variable

Syntax structure:

If condition:

print ' True '

Else

print ' False '

Boolean expression:

EG1:

If True:
print ' OK '
Else
print ' No '

EG2:

If 0:
print ' OK '
Else
print ' No

EG3:

If 13:
print ' OK '
Else
print ' No

EG4:

If ' Baidu ':
print ' OK '
Else
print ' No '

Relational Expressions:

10>9------True-----> Boolean expression 1 (True)

10<9------False----> Boolean expression 0 (false)

EG1:

Record=int (raw_input (' plz input your record: '))
If record>=90:-------------relational Expressions: relational operators
print ' good! '
Else
print ' bad!

EG2:

Sex=raw_input (' plz input your sex: ')
If sex== ' male ':-------------relationship expression: relational operator

print ' Man '
Else
print ' Woman '

Logical expressions:------------Learn to construct more complex expressions with logical expressions

And, or, binocular operators

Not single-mesh operator

EG1:

Sex=raw_input (' plz input your sex: ')
If not sex== ' male ':-------relational expression-----Logical expression------Boolean expression
print ' Man '
Else
print ' Woman '

EG2:

Sex=raw_input (' plz input your sex: ')
If sex== ' male ' or sex== ' m ' or sex== ' man ' or sex== ' man ':----or one is true;
print ' Man '
Else
print ' Woman '

12th. If branch statement expression constructs