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  • Python小技巧1

    原文: http://blog.csdn.net/jclass/article/details/6144647


    一. 打印并输出到文件

     
    >>> print("aa","bb"," 11 ","ddddd",sep='-',end='ok/t',file=open("c:/test.txt",'w'))
    >>> print("-" *40)#打印40个"-"
    >>> print("aa","bb"," 11 ","ddddd",sep='-',end='ok/t',file=open("c:/test.txt",'w'))
    >>> print("-" *40)#打印40个"-"

    二. 打印字典的值

    >>> d = {"a":1,"b":2}  
    >>> print('%(a)s...%(b)s' %d)
    1...2
    >>> s = ('%(a)s...%(b)s' %d)
    >>> s
    '1...2'
    >>> s = ['%(a)s...%(b)s' %d]
    >>> s
    ['1...2']
    >>> print("%(__builtins__)s...%(d)s" %vars())
    <module 'builtins' (built-in)>...{'a': 1, 'b': 2}
    >>> vars()
    {'__builtins__': <module 'builtins' (built-in)>, '__name__': '__main__', '__doc__': None, 'd': {'a': 1, 'b': 2}, '__package__': None}
    >>> locals()
    {'__builtins__': <module 'builtins' (built-in)>, '__name__': '__main__', '__doc__': None, 'd': {'a': 1, 'b': 2}, '__package__': None}
    >>> vars() is locals() #vars()无参数的情况等同locals()
    True
    >>> vars() == locals()
    True
    >>> a = vars()
    >>> b = locals()
    >>> a is b
    True
    >>> d = {"a":1,"b":2}
    >>> print('%(a)s...%(b)s' %d)
    1...2
    >>> s = ('%(a)s...%(b)s' %d)
    >>> s
    '1...2'
    >>> s = ['%(a)s...%(b)s' %d]
    >>> s
    ['1...2']
    >>> print("%(__builtins__)s...%(d)s" %vars())
    <module 'builtins' (built-in)>...{'a': 1, 'b': 2}
    >>> vars()
    {'__builtins__': <module 'builtins' (built-in)>, '__name__': '__main__', '__doc__': None, 'd': {'a': 1, 'b': 2}, '__package__': None}
    >>> locals()
    {'__builtins__': <module 'builtins' (built-in)>, '__name__': '__main__', '__doc__': None, 'd': {'a': 1, 'b': 2}, '__package__': None}
    >>> vars() is locals() #vars()无参数的情况等同locals()
    True
    >>> vars() == locals()
    True
    >>> a = vars()
    >>> b = locals()
    >>> a is b
    True


     

    三. pprint整洁打印

    >>> import pprint  
    >>> pprint.pprint(data)
    ('this is a string',
    [1, 2, 3, 4],
    ('more tuples', 1.0, 2.3, 4.5),
    'this is yet another string')
    >>> print(data)
    ('this is a string', [1, 2, 3, 4], ('more tuples', 1.0, 2.3, 4.5), 'this is yet another string')
    >>> pp = pprint.PrettyPrinter(indent=4) #缩进4空格
    >>> pp.pprint(data)
    ( 'this is a string',
    [1, 2, 3, 4],
    ('more tuples', 1.0, 2.3, 4.5),
    'this is yet another string')
    >>> import pprint
    >>> pprint.pprint(data)
    ('this is a string',
    [1, 2, 3, 4],
    ('more tuples', 1.0, 2.3, 4.5),
    'this is yet another string')
    >>> print(data)
    ('this is a string', [1, 2, 3, 4], ('more tuples', 1.0, 2.3, 4.5), 'this is yet another string')
    >>> pp = pprint.PrettyPrinter(indent=4) #缩进4空格
    >>> pp.pprint(data)
    ( 'this is a string',
    [1, 2, 3, 4],
    ('more tuples', 1.0, 2.3, 4.5),
    'this is yet another string')


     

    四. 打印输出重定向

    >>> import sys  
    >>> sys.stdout = open('c:/log123.txt','w')
    >>> print ("aa","bb","1111111112213123")
    >>> sys.stdout = sys.__stdout__
    >>> import sys
    >>> sys.stdout = open('c:/log123.txt','w')
    >>> print ("aa","bb","1111111112213123")
    >>> sys.stdout = sys.__stdout__


    >>> import sys
    >>> t = sys.stdout
    >>> sys.stdout = open("c:/log123.txt",'w')
    >>> print('1234abcd')
    >>> sys.stdout = t
    >>> print("11")
    11
    >>>
    >>> import sys
    >>> t = sys.stdout
    >>> sys.stdout = open("c:/log123.txt",'w')
    >>> print('1234abcd')
    >>> sys.stdout = t
    >>> print("11")
    11
    >>>


     

    五. with方式读取文件直到某行停止

    读取文件,直到某一行的文本等于"STOP"停止读取。否则,将一直读取下去。
    (注意:停止读取的行文本只能是iter()的第二个参数值,不能包含其他的,空格都不行)

    with open("c:/test.txt") as fp:  
    for line in iter(fp.readline,"STOP"):
    print(line)
    with open("c:/test.txt") as fp:
    for line in iter(fp.readline,"STOP"):
    print(line)


     

    六. 搜索目录树中包含有某个字符串的文件名的所有文件列表

    >>> import glob  
    >>> import fileinput
    >>> import os
    >>> import re
    >>> glob.glob("E:/cdr01")
    ['E:/cdr01']
    >>> glob.glob("E:/cdr01/*")#只返回当前cdr01下面的子目录名和文件名(带路径,但不包含目录树中的所有子目录与文件)
    ['E:/cdr01//20110113', 'E:/cdr01//20110114', 'E:/cdr01//20110115', 'E:/cdr01//20110116', 'E:/cdr01//20110117', 'E:/cdr01//20110118', 'E:/cdr01//20110119', 'E:/cdr01//20110120', 'E:/cdr01//20110121', 'E:/cdr01//20110122', 'E:/cdr01//20110123', 'E:/cdr01//20110124', 'E:/cdr01//cdr01.rar']
    >>> [(a,b,c) for a , b , c in os.walk("E:/cdr01")] #os.walk返回目录树中的所有目录与文件,他将每一目录的子目录与文件都按一个元组来返回。a代表当前搜索目录(或者子目录),b代表当前搜索目录下面所包含的子目录列表,c代表当前搜索目录下面的所有文件名列表。(不带路径(但可以通过与元组第一项进行拼接为目录或者文件路径),并且包含目录树中的所有子目录与文件)
    [('E:/cdr01', ['20110113', '20110114', '20110115', '20110116', '20110117', '20110118', '20110119', '20110120', '20110121', '20110122', '20110123', '20110124'], ['cdr01.rar']), ('E:/cdr01//20110113', [], ['20110113_6042488744.csv']), ('E:/cdr01//20110114', [], ['20110114_6042488744.csv']), ('E:/cdr01//20110115', [], ['20110115_6042488744.csv']), ('E:/cdr01//20110116', [], ['20110116_6042488744.csv']), ('E:/cdr01//20110117', [], ['20110117_6042488744.csv']), ('E:/cdr01//20110118', [], ['20110118_6042488744.csv']), ('E:/cdr01//20110119', [], ['20110119_6042488744.csv']), ('E:/cdr01//20110120', [], ['20110120_6042488744.csv']), ('E:/cdr01//20110121', [], ['20110121_6042488744.csv']), ('E:/cdr01//20110122', [], ['20110122_6042488744.csv']), ('E:/cdr01//20110123', [], ['20110123_6042488744.csv']), ('E:/cdr01//20110124', [], ['20110124_6042488744.csv'])]
    >>> list((os.path.join(a,f)) for a , b , c in os.walk("E:/cdr201101") for f in c if re.search('6042488744',os.path.basename(f))) #E:/cdr201101包含很多CSV文件,此方法将搜索目录树中的文件名包含字符串"6042488744"的文件,并将文件名与路径拼接作为绝对路径返回。
    ['E:/cdr201101//20110113//20110113_6042488744.csv', 'E:/cdr201101//20110114//20110114_6042488744.csv', 'E:/cdr201101//20110115//20110115_6042488744.csv', 'E:/cdr201101//20110116//20110116_6042488744.csv', 'E:/cdr201101//20110117//20110117_6042488744.csv', 'E:/cdr201101//20110118//20110118_6042488744.csv', 'E:/cdr201101//20110119//20110119_6042488744.csv', 'E:/cdr201101//20110120//20110120_6042488744.csv', 'E:/cdr201101//20110121//20110121_6042488744.csv', 'E:/cdr201101//20110122//20110122_6042488744.csv', 'E:/cdr201101//20110123//20110123_6042488744.csv', 'E:/cdr201101//20110124//20110124_6042488744.csv']
    >>> import glob
    >>> import fileinput
    >>> import os
    >>> import re
    >>> glob.glob("E:/cdr01")
    ['E:/cdr01']
    >>> glob.glob("E:/cdr01/*")#只返回当前cdr01下面的子目录名和文件名(带路径,但不包含目录树中的所有子目录与文件)
    ['E:/cdr01//20110113', 'E:/cdr01//20110114', 'E:/cdr01//20110115', 'E:/cdr01//20110116', 'E:/cdr01//20110117', 'E:/cdr01//20110118', 'E:/cdr01//20110119', 'E:/cdr01//20110120', 'E:/cdr01//20110121', 'E:/cdr01//20110122', 'E:/cdr01//20110123', 'E:/cdr01//20110124', 'E:/cdr01//cdr01.rar']
    >>> [(a,b,c) for a , b , c in os.walk("E:/cdr01")] #os.walk返回目录树中的所有目录与文件,他将每一目录的子目录与文件都按一个元组来返回。a代表当前搜索目录(或者子目录),b代表当前搜索目录下面所包含的子目录列表,c代表当前搜索目录下面的所有文件名列表。(不带路径(但可以通过与元组第一项进行拼接为目录或者文件路径),并且包含目录树中的所有子目录与文件)
    [('E:/cdr01', ['20110113', '20110114', '20110115', '20110116', '20110117', '20110118', '20110119', '20110120', '20110121', '20110122', '20110123', '20110124'], ['cdr01.rar']), ('E:/cdr01//20110113', [], ['20110113_6042488744.csv']), ('E:/cdr01//20110114', [], ['20110114_6042488744.csv']), ('E:/cdr01//20110115', [], ['20110115_6042488744.csv']), ('E:/cdr01//20110116', [], ['20110116_6042488744.csv']), ('E:/cdr01//20110117', [], ['20110117_6042488744.csv']), ('E:/cdr01//20110118', [], ['20110118_6042488744.csv']), ('E:/cdr01//20110119', [], ['20110119_6042488744.csv']), ('E:/cdr01//20110120', [], ['20110120_6042488744.csv']), ('E:/cdr01//20110121', [], ['20110121_6042488744.csv']), ('E:/cdr01//20110122', [], ['20110122_6042488744.csv']), ('E:/cdr01//20110123', [], ['20110123_6042488744.csv']), ('E:/cdr01//20110124', [], ['20110124_6042488744.csv'])]
    >>> list((os.path.join(a,f)) for a , b , c in os.walk("E:/cdr201101") for f in c if re.search('6042488744',os.path.basename(f))) #E:/cdr201101包含很多CSV文件,此方法将搜索目录树中的文件名包含字符串"6042488744"的文件,并将文件名与路径拼接作为绝对路径返回。
    ['E:/cdr201101//20110113//20110113_6042488744.csv', 'E:/cdr201101//20110114//20110114_6042488744.csv', 'E:/cdr201101//20110115//20110115_6042488744.csv', 'E:/cdr201101//20110116//20110116_6042488744.csv', 'E:/cdr201101//20110117//20110117_6042488744.csv', 'E:/cdr201101//20110118//20110118_6042488744.csv', 'E:/cdr201101//20110119//20110119_6042488744.csv', 'E:/cdr201101//20110120//20110120_6042488744.csv', 'E:/cdr201101//20110121//20110121_6042488744.csv', 'E:/cdr201101//20110122//20110122_6042488744.csv', 'E:/cdr201101//20110123//20110123_6042488744.csv', 'E:/cdr201101//20110124//20110124_6042488744.csv']


     

    七. 字符串转成字节数组,字节数组转成字节串

    >>> s = 'abcd123'  
    >>> b = bytearray(s,sys.stdin.encoding) #sys.stdin.encoding相当于locale.getdefaultlocale()[1]获得当前操作系统的编码方式
    >>> b
    bytearray(b'abcd123')
    >>> b = bytes(s,sys.stdin.encoding)
    >>> b
    b'abcd123'
    >>> s = 'abcd123'
    >>> b = bytearray(s,sys.stdin.encoding) #sys.stdin.encoding相当于locale.getdefaultlocale()[1]获得当前操作系统的编码方式
    >>> b
    bytearray(b'abcd123')
    >>> b = bytes(s,sys.stdin.encoding)
    >>> b
    b'abcd123'


    八. 字符串与字节的编码与解码

    >>> a = b'abc'  
    >>> a.decode() #字节解码为字符串
    'abc'
    >>> b = aa.encode() #字符串编码为字节
    >>> b
    b'abc'
    >>>
    >>> a = b'abc'
    >>> a.decode() #字节解码为字符串
    'abc'
    >>> b = aa.encode() #字符串编码为字节
    >>> b
    b'abc'
    >>>


     

    九. 处理zip压缩文件

    >>> import zipfile  
    >>> f = zipfile.ZipFile("E:/CodeBuilder.zip","r")
    >>> for name in f.namelist():
    data = f.read(name)
    print(name,len(data),repr(data[:10]))
    >>> f.close()
    >>> import zipfile
    >>> f = zipfile.ZipFile("E:/CodeBuilder.zip","r")
    >>> for name in f.namelist():
    data = f.read(name)
    print(name,len(data),repr(data[:10]))
    >>> f.close()


    >>> import zipfile
    >>> z = zipfile.ZipFile("E:/test1.zip","w") #创建zip压缩文件包
    >>> z.write("E:/testSqliteDB.db.txt") #压缩一个txt文件
    >>> z.close()
    >>> z = zipfile.ZipFile("E:/test1.zip","r") #读取zip压缩文件包
    >>> z.extractall()#解压到当前目录,extract可以具体指定解压哪个文件到哪个目录
    >>> z.extractall("E:/123/")#解压到指定目录
    >>> z.close()
    >>> import os
    >>> os.getcwd() #getcwd()可以查看解压的当前目录位置
    'C://Python31'
    >>> import zipfile
    >>> z = zipfile.ZipFile("E:/test1.zip","w") #创建zip压缩文件包
    >>> z.write("E:/testSqliteDB.db.txt") #压缩一个txt文件
    >>> z.close()
    >>> z = zipfile.ZipFile("E:/test1.zip","r") #读取zip压缩文件包
    >>> z.extractall()#解压到当前目录,extract可以具体指定解压哪个文件到哪个目录
    >>> z.extractall("E:/123/")#解压到指定目录
    >>> z.close()
    >>> import os
    >>> os.getcwd() #getcwd()可以查看解压的当前目录位置
    'C://Python31'


     

    十. glob遍历文件夹下面的所有文件并读取内容

    >>> import fileinput  
    >>> import glob
    >>> for line in fileinput.input(glob.glob("E:/TestFolder/*.txt")):
    print("File name:" + fileinput.filename() + " line length:" + str(len(line)))
    >>> fileinput.close()
    >>> import fileinput
    >>> import glob
    >>> for line in fileinput.input(glob.glob("E:/TestFolder/*.txt")):
    print("File name:" + fileinput.filename() + " line length:" + str(len(line)))
    >>> fileinput.close()


     

    十一. shutil拷贝目录树

    >>> import shutil  
    >>> shutil.copytree("E:/TestFolder","F:/TestFolder-bak")
    >>> shutil.copytree("E:/TestFolder","xx") #在TestFolder文件夹里面创建XX目录,并拷贝TestFolder目录到XX目录
    >>> import shutil
    >>> shutil.copytree("E:/TestFolder","F:/TestFolder-bak")
    >>> shutil.copytree("E:/TestFolder","xx") #在TestFolder文件夹里面创建XX目录,并拷贝TestFolder目录到XX目录


     

    十二. 获得文件大小的两种方式(二进制读取)

    >>> import os  
    >>> os.stat(f).st_size
    4753
    >>> os.path.getsize(f)
    4753
    >>> import os
    >>> os.stat(f).st_size
    4753
    >>> os.path.getsize(f)
    4753


     

    十三. mmap 模块提供了操作系统内存映射函数的接口,可以映射字符串与文件内容

    可以执行譬如查找、统计、写入等一些操作,但就是基于字节的。

    >>> map = mmap.mmap(-1,13)  
    >>> map.write(b"Hello world!")
    >>> map.readline()
    b'/x00'
    >>> map.seek(0)
    >>> map.readline()
    b'Hello world!/x00'
    >>> map.seek(0)
    >>> map.find(b'w')
    6
    >>> map.close()
    >>> map = mmap.mmap(-1,13)
    >>> map.write(b"Hello world!")
    >>> map.readline()
    b'/x00'
    >>> map.seek(0)
    >>> map.readline()
    b'Hello world!/x00'
    >>> map.seek(0)
    >>> map.find(b'w')
    6
    >>> map.close()


     

    十四. dis反编译对象为字节码

    >>> import dis  
    >>> def showMsg(xx):
    print("abc")


    >>> dis.dis(showMsg)
    2 0 LOAD_GLOBAL 0 (print)
    3 LOAD_CONST 1 ('abc')
    6 CALL_FUNCTION 1
    9 POP_TOP
    10 LOAD_CONST 0 (None)
    13 RETURN_VALUE
    >>> import dis
    >>> def showMsg(xx):
    print("abc")


    >>> dis.dis(showMsg)
    2 0 LOAD_GLOBAL 0 (print)
    3 LOAD_CONST 1 ('abc')
    6 CALL_FUNCTION 1
    9 POP_TOP
    10 LOAD_CONST 0 (None)
    13 RETURN_VALUE



    十五。profile 与 cProfile分析程序执行性能

    profile 模块是标准 Python 分析器,用Python写的。
    而cProfile是用C写的,运行起来比profile快,官方推荐用cProfile.

    pstats可以处理分析报告。

    >>> import profile  
    >>> def testss(n):
    i = 0
    for i in range(n):
    i = i + 1
    return i

    >>> profile.run("testss(1000000)")
    5 function calls in 0.269 CPU seconds

    Ordered by: standard name

    ncalls tottime percall cumtime percall filename:lineno(function)
    1 0.000 0.000 0.266 0.266 :0(exec)
    1 0.002 0.002 0.002 0.002 :0(setprofile)
    1 0.266 0.266 0.266 0.266 <pyshell#3>:1(testss)
    1 0.000 0.000 0.266 0.266 <string>:1(<module>)
    0 0.000 0.000 profile:0(profiler)
    1 0.000 0.000 0.269 0.269 profile:0(testss(1000000))


    >>> import cProfile
    >>> cProfile.run("testss(1000000)") #分析速度快些
    4 function calls in 0.212 CPU seconds

    Ordered by: standard name

    ncalls tottime percall cumtime percall filename:lineno(function)
    1 0.212 0.212 0.212 0.212 <pyshell#3>:1(testss)
    1 0.000 0.000 0.212 0.212 <string>:1(<module>)
    1 0.000 0.000 0.212 0.212 {built-in method exec}
    1 0.000 0.000 0.000 0.000 {method 'disable' of '_lsprof.Profiler' objects}
    >>> import profile
    >>> def testss(n):
    i = 0
    for i in range(n):
    i = i + 1
    return i

    >>> profile.run("testss(1000000)")
    5 function calls in 0.269 CPU seconds

    Ordered by: standard name

    ncalls tottime percall cumtime percall filename:lineno(function)
    1 0.000 0.000 0.266 0.266 :0(exec)
    1 0.002 0.002 0.002 0.002 :0(setprofile)
    1 0.266 0.266 0.266 0.266 <pyshell#3>:1(testss)
    1 0.000 0.000 0.266 0.266 <string>:1(<module>)
    0 0.000 0.000 profile:0(profiler)
    1 0.000 0.000 0.269 0.269 profile:0(testss(1000000))


    >>> import cProfile
    >>> cProfile.run("testss(1000000)") #分析速度快些
    4 function calls in 0.212 CPU seconds

    Ordered by: standard name

    ncalls tottime percall cumtime percall filename:lineno(function)
    1 0.212 0.212 0.212 0.212 <pyshell#3>:1(testss)
    1 0.000 0.000 0.212 0.212 <string>:1(<module>)
    1 0.000 0.000 0.212 0.212 {built-in method exec}
    1 0.000 0.000 0.000 0.000 {method 'disable' of '_lsprof.Profiler' objects}


     

    pstats处理分析报告:

    >>> import pstats  
    >>> pr = profile.Profile()
    >>> pr.run("testss(1000000)")
    <profile.Profile object at 0x0143C8D0>
    >>> p = pstats.Stats(pr)
    >>> pstats = p.sort_stats("time") #按时间排序
    >>> pstats.print_stats() #打印在profile.run()中形成的分析报告
    5 function calls in 38.856 CPU seconds

    Ordered by: internal time

    ncalls tottime percall cumtime percall filename:lineno(function)
    1 25.843 25.843 25.843 25.843 :0(setprofile)
    1 12.760 12.760 38.856 38.856 profile:0(testss(1000000))
    1 0.253 0.253 0.253 0.253 <pyshell#3>:1(testss)
    1 0.000 0.000 0.253 0.253 :0(exec)
    1 0.000 0.000 0.253 0.253 <string>:1(<module>)
    0 0.000 0.000 profile:0(profiler)


    <pstats.Stats object at 0x0143C330>
    >>> import pstats
    >>> pr = profile.Profile()
    >>> pr.run("testss(1000000)")
    <profile.Profile object at 0x0143C8D0>
    >>> p = pstats.Stats(pr)
    >>> pstats = p.sort_stats("time") #按时间排序
    >>> pstats.print_stats() #打印在profile.run()中形成的分析报告
    5 function calls in 38.856 CPU seconds

    Ordered by: internal time

    ncalls tottime percall cumtime percall filename:lineno(function)
    1 25.843 25.843 25.843 25.843 :0(setprofile)
    1 12.760 12.760 38.856 38.856 profile:0(testss(1000000))
    1 0.253 0.253 0.253 0.253 <pyshell#3>:1(testss)
    1 0.000 0.000 0.253 0.253 :0(exec)
    1 0.000 0.000 0.253 0.253 <string>:1(<module>)
    0 0.000 0.000 profile:0(profiler)


    <pstats.Stats object at 0x0143C330>


     

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  • 原文地址:https://www.cnblogs.com/lanzhi/p/6468584.html
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