Python 基础知识点总结

try:
    print ‘try...‘
    r = 10/0
    print ‘result:‘,r
except ZeroDivisionError,e:
    print ‘except:‘,e
finally:
    print ‘finally...‘

try:
    print ‘try...‘
    r = 10/int(‘a‘)
    print ‘result:‘,r
except ValueError,e:
    print ‘ValueError‘,e
except ZeroDivisionError,e:
    print ‘ZeroDivisionError:‘,e
else:
    print ‘no error!‘
finally:
    print ‘finally...‘

def foo(s):
    return 10 / int(s)
def bar(s):
    return foo(s) * 2
def main():
    try:
        bar(‘0‘)
    except StandardError, e:
        logging.exception(e)
main()
print ‘END‘

C:\Python27\python.exe C:/Aran_Files/Git/PythonLearn/2015-04-14.py
ERROR:root:integer division or modulo by zero
aran
Traceback (most recent call last):
aran
END
  File "C:/Aran_Files/Git/PythonLearn/2015-04-14.py", line 87, in main
    bar(‘0‘)
  File "C:/Aran_Files/Git/PythonLearn/2015-04-14.py", line 83, in bar
    return foo(s) * 2
  File "C:/Aran_Files/Git/PythonLearn/2015-04-14.py", line 80, in foo
    return 10 / int(s)
ZeroDivisionError: integer division or modulo by zero
Process finished with exit code 0

def func2(s):
    assert s!=0,‘n is zero‘
    return s
func2(0)

f = open(‘Stream.txt‘,‘r‘)
print f.read()
f.close()    

try:
    f = open(‘Streasm.txt‘,‘r‘)
    print f.read()
except IOError,e:
    pass
finally:
    if f:
        f.close()

with open(‘Stream.txt‘,‘r‘) as f:
    print f.read()

with open(‘text.txt‘,‘rb‘) as f:
    print f.read().decode(‘gbk‘)

import codecs
with codecs.open(‘text.txt‘,‘r‘,‘gbk‘) as f:
    print f.read()

with open(‘Stream.txt‘,‘w‘) as f:
    f.write(‘Hello,world‘)

def search(str,path=os.path.abspath(‘.‘)):
    for x in os.listdir(path):
        if os.path.isdir(x):
            search(str,os.path.join(path,x))
        else:
            if str in x:
                print os.path.join(path,x)

try:
    import CPickle as pickle
except ImportError:
    import pickle
d = dict(name=‘Bob‘,age=20,score=88)
dp = pickle.dumps(d)
print dp
d = pickle.loads(dp)
print d

d = dict(name=‘Bob‘,age=20,score=88)
with open(‘dump.txt‘,‘wb‘) as f:
    pickle.dump(d,f)
with open(‘dump.txt‘,‘rb‘) as f:
    d = pickle.load(f)
print d

import json
class Student(object):
    def __init__(self, name, score):
        self.name = name
        self.score = score
s = Student(‘Bob‘, 88)
#序列化
print(json.dumps(s.__dict__))
#反序列化
print(json.loads(json.dumps(s.__dict__),object_hook=lambda d:Student(d[‘name‘],d[‘score‘])))

from multiprocessing import Pool
import os,time,random
def time_task(name):
    print ‘Run task %s(%s)...‘ %(name,os.getpid())
    start = time.time()
    time.sleep(random.random()*10)
    end = time.time()
    print ‘Task %s runs %0.2f seconds.‘%(name,(end-start))
if __name__ == ‘__main__‘:
    print ‘Parent process %s.‘ % os.getpid()
    p = Pool(4)
    for i in range(5):
        p.apply_async(time_task,args=(i,))
    print ‘Waiting for all subprocesses done...‘
    p.close()
    p.join()
    print ‘All subprocesses done.‘
运行结果：
Parent process 11232.
Waiting for all subprocesses done...
Run task 0(10824)...
Run task 1(8960)...
Run task 2(8216)...
Run task 3(7340)...
Task 2 runs 0.24 seconds.
Run task 4(8216)...
Task 3 runs 2.15 seconds.
Task 1 runs 5.85 seconds.
Task 0 runs 8.99 seconds.
Task 4 runs 9.88 seconds.
All subprocesses done. 

from multiprocessing import Process, Queue
import os, time, random
# 写数据进程执行的代码:
def write(q):
    for value in [‘A‘, ‘B‘, ‘C‘]:
        print ‘Put %s to queue...‘ % value
        q.put(value)
        time.sleep(random.random())
# 读数据进程执行的代码:
def read(q):
    while True:
        value = q.get(True)
        print ‘Get %s from queue.‘ % value
if __name__==‘__main__‘:
    # 父进程创建Queue，并传给各个子进程：
    q = Queue()
    pw = Process(target=write, args=(q,))
    pr = Process(target=read, args=(q,))
    # 启动子进程pw，写入:
    pw.start()
    # 启动子进程pr，读取:
    pr.start()
    # 等待pw结束:
    pw.join()
    # pr进程里是死循环，无法等待其结束，只能强行终止:
    pr.terminate()
运行结果：
Put A to queue...
Get A from queue.
Put B to queue...
Get B from queue.
Put C to queue...
Get C from queue.

print threading.current_thread().name
def namePrint(ID):
    print threading.current_thread().name , ID
t = threading.Thread(target=namePrint, name = ‘Threadtest‘,args=(1,))
t.start()
t.join()

结果：
MainThread
Threadtest 1

balance = 0
lock = threading.Lock()
def changeBalance(n):
    global balance
    balance =  n
def run_thread(n):
    lock.acquire()
    try:
        changeBalance(n)
    finally:
        lock.release()
t1 = threading.Thread(target=run_thread,args=(100,))
t2 = threading.Thread(target=run_thread,args=(20,))
t1.start()
t2.start()
t1.join()
t2.join()
print balance

import threading
dict = {}
def process_print():
    print ‘Hello, %s (in %s)‘ % (dict[threading.current_thread().name], threading.current_thread().name)
def process_thread(name):
    dict[threading.current_thread().name] = name
    process_print()
t1 = threading.Thread(target= process_thread, args=(‘Alice‘,))
t2 = threading.Thread(target= process_thread, args=(‘Bob‘,))
t1.start()
t2.start()
t1.join()
t2.join()