python之三-statements and functions

1.if

if condiction1 and condition2:

  action1

elif condition3:

  action2

else:

  action3

<,<=,>,>=,==,!=,in

x=2;y=3;L=[0,1,2]

if (1<x<=3 and 4>y>=2) or (1==1or o!=1) or 1 in L:

  print 'Hello world'

 

2.while

while x<=4:

  ...

3.for

 for item i in set s :

  ...

for i in range(1,7):

 ...

4.functions

可以有多个return

5.multiple assignment

x,y=2,3

5.help info for functions

6.Scope Rules

Build-in(Python)

  predefined names(len,open,execfile,etc.) and types

Global(module)

  Names assigned at the top level of a module, or directly in the interpreter

  Names declared global in a function

Local(function)

  Names assigned inside a function definition or loop

7.exception handling

类似于java

try:

except IOError:

finally:

 

def factorial(n)

  if n<0

    raise ValueError,"Expected non-negative number"

.....

 

8.File Objects

file.open()

file.read()

file.write()

file.readlines

file.readline