Python core Programming the next day

1. Standard input and output:

Import Sys

saveout=sys.stdout# Saving current output state

Logfile=open (' E://log.txt ', ' R ') # Open File

sys.stdout=logfile# Defining output files

sys.stderr=logfile# defining an exception output file

print ' Helloword ' #向日志写入 ' Helloword '

Raise IOError, ' helloword ' # ' writes exception information to the log ' Helloword '

sys.stdout=saveout# return to normal output

print ' Hellword ' #控制台输出helloword

2. Logical operator: and OR not

3, the expression by priority: *,/,/,%, +,-

4, Not Equal! = (<>)

5, >>5<6<7

>>true

6, >>true+1

>>2

>>false+1

>>1

7, Increment assignment: A+=5,x*=6 ...

8. Numeric type: Signed integer, Boolean, constant integer, floating point, plural

9. Decimal package represents the decimals floating point type

>>decimal. Decimal (' 1.1 ')

>>1.1

10. String +, *

11, a= ' Helloword '

>>len (a)

>>9

>>a[0:]

>> ' Helloword '

>>A[-1]

>> ' d '

10, tuple tuple a= (1,2,3,4,5,6,7)

11. Dictionary: Items (), values (), keys ()

Print Layout

>>a= (1,2,3,4,5,6,7,8,9)

>>for i in range (Len (a)):

.. print a,

>>1 2 3 4 5 6 7 8 9

>>print ' Hello%d%d\

...%s '%[1,2, ' Helloword ' *100]

>>hello12helloword .....

>>for i in range (0,1,2):

... print I,

>>0 1 2

>>for I, J in Enumerate (a):

... print I,j

>>0 1

>>1 2

>>, .....

13. List parsing

>>p=[x for x in range (10)]

>>p

>>[1,2,3,4,5,6,7,8,9,10]

>>p=[x for x in range (ten) if not x%2]

>>p

>>[0,2,4,6,8]

14. File Operation:

Try

File=open (' E://log.txt ', ' R ') #默认打开方式为读, W for write, A for append

For line in File.readlines (): #for the line in file:

Print line,

Except Ioerror,e#raise IOError, ' Helloword '

Print E

File.close ()

Python core Programming the next day