python︱函数、for、if、_name_、迭代器、防范报错、类定义、装饰器、argparse模块

def myadd(a=1,b=100):
    result = 0
    i = a
    while i <= b:    # 默认值为1+2+3+……+100
        result += i    
        i += 1
    return result

为真时的结果 if 判定条件 else 为假时的结果  

1 if 5>3 else 0

conf = (11,2,3)
[i for i in conf if i > 2]
>>> [11, 3]

conf = (11,2,3)
[i for i, c in enumerate(conf) if c > 2]
>>> [0, 2]

>>> filter(lambda x : x%2 == 0,[1,2,3,4,5])  
[2, 4]  

def filter(bool_func,seq):  
    filtered_seq = []  
    for eachItem in seq:  
        if bool_func(eachItem):  
            filtered_seq.append(eachItem)  
    return filtered_seq  

>>> map(lambda x : None,[1,2,3,4])  
[None, None, None, None]  
>>> map(lambda x : x * 2,[1,2,3,4])  
[2, 4, 6, 8]  
>>> map(lambda x : x * 2,[1,2,3,4,[5,6,7]])  
[2, 4, 6, 8, [5, 6, 7, 5, 6, 7]]  
>>> map(lambda x : None,[1,2,3,4])  
[None, None, None, None]  

>>> def map(func,seq):  
    mapped_seq = []  
    for eachItem in seq:  
        mapped_seq.append(func(eachItem))  
    return mapped_seq  

>>> reduce(lambda x,y : x + y,[1,2,3,4])  
10  
>>> reduce(lambda x,y : x + y,[1,2,3,4],10)  
20  

def reduce(bin_func,seq,initial=None):  
    lseq = list(seq)  
    if initial is None:  
        res = lseq.pop(0)  
    else:  
        res = initial  
    for eachItem in lseq:  
        res = bin_func(res,eachItem)  
    return res  

for letter in 'Python':     # 第一个实例
   print '当前字母 :', letter

当前字母 : P
当前字母 : y
当前字母 : t
当前字母 : h
当前字母 : o
当前字母 : n

fruits = ['banana', 'apple',  'mango']
for fruit in fruits:        # 第二个实例
   print '当前字母 :', fruit

for num in range(10,20):  # 迭代 10 到 20 之间的数字
   for i in range(2,num): # 根据因子迭代
      if num%i == 0:      # 确定第一个因子
         j=num/i          # 计算第二个因子
         print '%d 等于 %d * %d' % (num,i,j)
         break            # 跳出当前循环
   else:                  # 循环的 else 部分
      print num, '是一个质数'

import numpy as np
l=[("f1",'g1'),("f2","g2")]
h=['go1','go2']

In [17]:{iter:np.zeros(2) for iter,_ in l }
Out[17]: {'f1': array([ 0.,  0.]), 'f2': array([ 0.,  0.])}

In [18]:[{iter:np.zeros(2) for iter,_ in l } for _ in h]
Out[18]: 
[{'f1': array([ 0.,  0.]), 'f2': array([ 0.,  0.])},
 {'f1': array([ 0.,  0.]), 'f2': array([ 0.,  0.])}]

#!/usr/bin/python
count = 0
while (count < 9):   
   print 'The count is:', count    count = count + 1
print "Good bye!"

The count is: 0
The count is: 1
The count is: 2
The count is: 3
The count is: 4
The count is: 5
The count is: 6
The count is: 7
The count is: 8
Good bye!

# continue 和 break 用法i = 1
while i < 10:      i += 1    if i%2 > 0:     
# 非双数时跳过输出        
continue    print i         
# 输出双数2、4、6、8、10i = 1
while 1:            
# 循环条件为1必定成立   
 print i        
i += 1    
if i > 10:    
 # 当i大于10时跳出循环  
       break

#!/usr/bin/python
count = 0
while count < 5:   
  print count, " is  less than 5"   count = count + 1
else:   
  print count, " is not less than 5"

>>>
0 is less than 5
1 is less than 5
2 is less than 5
3 is less than 5
4 is less than 5
5 is not less than 5

nfc = ["Packers", "49ers"]
afc = ["Ravens", "Patriots"]
for teama, teamb in zip(nfc, afc):
     print teama + " vs. " + teamb
>>> Packers vs. Ravens
>>> 49ers vs. Patriots

teams = ["Packers", "49ers", "Ravens", "Patriots"]
for index, team in enumerate(teams):
    print index, team
>>> 0 Packers
>>> 1 49ers
>>> 2 Ravens
>>> 3 Patriots

numbers = [1,2,3,4,5,6]
even = []
for number in numbers:
    if number%2 == 0:
        even.append(number)

teams = ["Packers", "49ers", "Ravens", "Patriots"]
print {key: value for value, key in enumerate(teams)}
>>> {'49ers': 1, 'Ravens': 2, 'Patriots': 3, 'Packers': 0}

from itertools import combinations
teams = ["Packers", "49ers", "Ravens", "Patriots"]
for game in combinations(teams, 2):
    print game
>>> ('Packers', '49ers')
>>> ('Packers', 'Ravens')
>>> ('Packers', 'Patriots')
>>> ('49ers', 'Ravens')
>>> ('49ers', 'Patriots')
>>> ('Ravens', 'Patriots')

def XXXX():
#body
print "asdf"

def XXXX():
#body
if __name__="__main__":
print "asdf"

py> x = 23
py> assert x > 0, "x is not zero or negative"
py> assert x%2 == 0, "x is not an even number"
Traceback (most recent call last):
File "", line 1, in 
AssertionError: x is not an even number

try:
    f = open('xxx')
except:
    print 'fail to open'
    exit(-1)

try:
<语句>        #运行别的代码
except <名字>：
<语句>        #如果在try部份引发了'name'异常
except <名字>，<数据>:
<语句>        #如果引发了'name'异常，获得附加的数据
else:
<语句>        #如果没有异常发生

try:
    print('I am sure no exception is going to occur!')
except Exception:
    print('exception')
else:
    # 这里的代码只会在try语句里没有触发异常时运行,
    # 但是这里的异常将 *不会* 被捕获
    print('This would only run if no exception occurs. And an error here '
          'would NOT be caught.')
finally:
    print('This would be printed in every case.')

# Output: I am sure no exception is going to occur!
# This would only run if no exception occurs.
# This would be printed in every case.

try:
    1/0
except Exception, e:
    print 'str(Exception):\t', str(Exception)
    print 'str(e):\t\t', str(e)
    print 'repr(e):\t', repr(e)
    print 'e.message:\t', e.message
    print 'traceback.print_exc():'; traceback.print_exc()
    print 'traceback.format_exc():\n%s' % traceback.format_exc()

def this_fails():
    x = 1/0

try:
    this_fails()
except :
    print('Handling run-time error:')
    raise
print(1)

import logging
logging.basicConfig(filename = os.path.join(os.getcwd(), 'log.txt'), level = logging.DEBUG)
log = logging.getLogger('root')
try:
    a===b
except:
    log.exception('exception') #异常信息被自动添加到日志消息中

ERROR:root:exception
Traceback (most recent call last):
  File "test.py", line 12, in <module>
    a==b
NameError: name 'a' is not defined

import logging
import unittest
class lgtest(unittest.TestCase):
    logging.basicConfig(filename='../LOG/'+__name__+'.log',format='[%(asctime)s-%(filename)s-%(levelname)s:%(message)s]', level = logging.DEBUG,filemode='a',datefmt='%Y-%m-%d%I:%M:%S %p')

    def test(self):

        logging.error("这是一条error信息的打印")
        logging.info("这是一条info信息的打印")
        logging.warning("这是一条warn信息的打印")
        logging.debug("这是一条debug信息的打印")
if __name__=='__main__':
    unittest.main()

# 信息写入log
import logging
from logging import handlers
class Logger(object):
    level_relations = {
        'debug':logging.DEBUG,
        'info':logging.INFO,
        'warning':logging.WARNING,
        'error':logging.ERROR,
        'crit':logging.CRITICAL
    }#日志级别关系映射

    def __init__(self,filename,level='info',when='D',backCount=15,\
                 fmt='%(asctime)s - %(levelname)s: %(message)s'):
        self.logger = logging.getLogger(filename)   # 创建log文件
        format_str = logging.Formatter(fmt)#设置日志格式
        self.logger.setLevel(self.level_relations.get(level))#设置日志级别
        if not self.logger.handlers:
            sh = logging.StreamHandler()  # 初始化 1 ，往屏幕上输出
            sh.setFormatter(format_str)   #  设置屏幕上显示的格式
            th = handlers.TimedRotatingFileHandler(filename=filename,when=when,\
                                                   backupCount=backCount,encoding='utf-8')
            
            th.setFormatter(format_str)#设置文件里写入的格式
            self.logger.addHandler(sh) #把对象加到logger里
            self.logger.addHandler(th)
if __name__ == '__main__':
    log = Logger('all.log',level='debug')
    log.logger.debug('debug')
    log.logger.info('info')
    log.logger.warning('警告')
    log.logger.error('报错'', exc_info=True)
    log.logger.critical('严重')
    Logger('error.log', level='error').logger.error('error')

2018-03-13 21:06:46,092 - DEBUG: debug
2018-03-13 21:06:46,092 - INFO: info
2018-03-13 21:06:46,092- WARNING: 警告
2018-03-13 21:06:46,099 - ERROR: 报错
2018-03-13 21:06:46,099- CRITICAL: 严重
2018-03-13 21:06:46,100 - ERROR: error

# 正常的self.logger.handlers长什么样子：
[<logging.StreamHandler at 0x12eba1e3128>,
 <logging.handlers.TimedRotatingFileHandler at 0x12eba1e3160>]

# 不正常的self.logger.handlers长什么样子：
[<logging.StreamHandler at 0x12eba1e3128>,
 <logging.handlers.TimedRotatingFileHandler at 0x12eba1e3160>,
 [<logging.StreamHandler at 0x12eba1e3128>,
 <logging.handlers.TimedRotatingFileHandler at 0x12eba1e3160>,]

import logging
logging.basicConfig(level=logging.INFO,
                   format='%(asctime)s  %(message)s',
                   datefmt='%a, %d %b %Y %H:%M:%S +0000',
                   filename='my.log')

logging.info('this is a info')
try:
    do
except Exception:
    logging.error('There are something wrong', exc_info=True)

logging.info('continue')


# 报错信息暴露
Sun, 01 Jul 2018 21:10:53 +0000  There are something wrong
Traceback (most recent call last):
  File "learn.py", line 9, in <module>
    do
NameError: name 'do' is not defined
Sun, 01 Jul 2018 21:10:53 +0000  continue

version: 1
formatters:
  simple:
    format: "%(message)s"
  more:
    format: "%(asctime)s - %(levelname)s - %(message)s"
handlers:
  console:
    class : logging.StreamHandler
    formatter: simple
    level: INFO
    stream: ext://sys.stdout
  file:
    class: logging.FileHandler
    formatter: more
    level: DEBUG
    filename: debug.log
loggers:
  mainlogger:
    level: DEBUG
    handlers: [console, file]
  root:
    level: DEBUG
    handlers: [console]

import logging
import logging.config
import yaml
import a

with open('config.yaml', 'r', encoding='utf-8') as f:
    config = yaml.load(f)
    logging.config.dictConfig(config)

logging.info('main file log')
a.run()

ith open("x.txt") as f:
    data = f.read()

with open("x.txt") as f1, open('xxx.txt') as f2:
    do something with f1,f2

try:
    with open( "a.txt" ) as f :
        do something
except xxxError:
    do something about exception

if pretrained_model not in self._models:
    raise ValueError(
        'The n_class needs to be supplied as an argument.')

raise RuntimeError('testError')

class <类名>:
    <语句>

class save_def(object):

    def __init__(self, name, score):
        self.name = name
        self.score = score

initialization = save_def（name,score）

initialization.other = "other"

class save_def(object):
    def __init__(self, name, score):
        self.name = name
        self.score = score
        
	def function1(self,dataframe):
	temp_data = type(dataframe[self.name])
	return temp_data 

initialization = save_def（name,score）
 initialization.function1(dataframe)

>>>def function1(name,dataframe):
	temp_data = type(dataframe[name])
	return temp_data 

>>>function1(name,dataframe)

class save_def(object):
    def __init__(self, name, score):
        self.name = name
        self.score = score
        
	def function1(self,dataframe):
	temp_data = type(dataframe[self.name])
	return temp_data 

	def function2(self):
		temp_data2 = self.function1(dataframe.ix[self.score>10,:])

import argparse
import ast
parser = argparse.ArgumentParser()
parser.add_argument("-t", "--t2s",type=ast.literal_eval,default = False, help=" True False")
parser.add_argument("-f", "--filename",default = '7w.csv', help="data file path and the format must utf-8 or gbk")
args = parser.parse_args()

if args.t2s:
    print('yes')

    parser.add_argument(
        "--show-mask-heatmaps",
        dest="show_mask_heatmaps",
        help="Show a heatmap probability for the top masks-per-dim masks",
        action="store_true",
    )

parser.add_argument('-c', action='store_true')
#python test.py -c         => c是true（触发）
#python test.py             => c是false（无触发）

globel name 'xxx' is not defined

import datetime
print(datetime.datetime.now())

from datetime import datetime
print(datetime.now())

from import : 从车里把矿泉水拿出来，给我
import : 把车给我

def func(name):
    def inner_func(age):
        print 'name:', name, 'age:', age
    return inner_func

bb = func('the5fire')
bb(26)  # >>> name: the5fire age: 26

def outer(function):
    def inner():
        print("执行function之前可以进行额外操作")
        result = function()
        print("执行function之后还可以进行额外操作")
        result *= 2        # 对function的返回值本身进行额外操作
        return result      # 返回‘加强’后的结果
    return inner

def wait_for_deco():
    return 1024

decorated = outer(wait_for_deco)
print decorated()
# 输出
2048

def function1(function):
	return function() + 1
# function作为参数传入，且这个参数名称是任意的，跟普通参数一致，需要对齐，函数也要写function

def function2():
	return 2
#这样的装饰器，一般不传入参数

# 使用
>>> function1(function2)
>>> 3
# 其中，不能写成function1(function2())

def outer(function):
    def inner():
        print("执行function之前可以进行额外操作")
        result = function()
        print("执行function之后还可以进行额外操作")
        result *= 2        # 对function的返回值本身进行额外操作
        return result      # 返回‘加强’后的结果
    return inner

@outer
def wait_for_deco():
    return 1024

print wait_for_deco()
# 输出
2048

# 例如为下面的函数写一个装饰器，应该在内部的wapper中按原样传递参数
def decorator(func):
    def wrapper(x, y)
      ret = func(x, y)    # 原函数的返回值
      return ret*2        # 原函数的结果“加强”后再返回
    return wrapper

@decorator
def wait_for_deco(x, y):
  return x + y

print(wait_for_deco(1, 2))

# 输出
6

def decorator(func):
    def wrapper(*args, **kwargs)
      ret = func(*args, **kwargs)
      return ret*2
    return wrapper

@decorator
def wait_for_deco_a(x, y):
  return x + y

@decorator
def wait_for_deco_b(x, y, z):
  return x + y + z

print(wait_for_deco_a(1, 2))
6
print(wait_for_deco_b(1, 2, 3))
12

def function2(function):
	# 因为要传入参数，所以下面的def 就相当于在写了一次_function2，但也不是简单的加个def，其中_代表，专属于函数内
    def _function2(b):
	    # 并不能写出：function2(function)
        a = function(b)
        return a + 1
    return _function2
# 返回的是函数本身

@function2
def function1(b):
    return b + 1

function2(function1)

def mydec(is_print):
    def mydec_f(func):
        def mydec_a(*args, **kwargs):
            r = func(*args, **kwargs)
            if is_print:
                print("结果是:{}".format(r))
            else:
                print("不打印结果")
        return mydec_a
    return mydec_f
 
@mydec(True)
def mysum(a, b): 
    c = a + b 
    return c
@mydec(False)
def mysum2(a, b, c): 
    d = a + b + c 
    return d
 
mysum(1, 2)
mysum2(1, 2, 3)


>>>结果是:3

class mycls():
    def __init__(self):
        print("类初始化了")
              
    @staticmethod
    def test1():
        print("我是mycls.test1")
                     
    @staticmethod
    def test2():
        print("我是mycls.test2")
 
  
# 装饰器
def mydec(cls):
    def mydec_f(func):
        def mydec_a(*args, **kwargs):
            cls.test1()
            r = func(*args, **kwargs)
            print("结果是:{}".format(r))
            cls.test2()
        return mydec_a
    return mydec_f
 
@mydec(mycls)
def mysum(a, b): 
    c = a + b 
    return c
@mydec(mycls)
def mysum2(a, b, c): 
    d = a + b + c 
    return d
 
mysum(1, 2)
mysum2(1, 2, 3)

我是mycls.test1
结果是:3
我是mycls.test2
我是mycls.test1
结果是:6
我是mycls.test2