Python基础学习5

函数学习要点：
1、函数基本操作：调用、创建、可变长参数（在方法定义中可以使用个数不确定的参数，不按顺序传参用关键字，不固定参数个数定义为fun(first,*other))、变量作用域
2、匿名函数（Lambda函数）
3、函数迭代器、生成器
4、函数闭包、装饰器
5、内建函数
6、自定义上下文管理器
实践操作代码：
未使用函数时代码

# 读取人物名称，name.txt是创建在代码路径下人物txt文档
f = open('name.txt',encoding='utf-8')
data = f.read()
data0 = data.split('|')
print(type(data))
print(data0)

# 读取兵器名称，weapon.txt是创建在代码路径下兵器txt文档
f2 = open('weapon.txt',encoding='utf-8')
i = 1
for  line in f2.readlines():
    if i % 2 == 1:
        print(line.strip('\n'))
    i += 1

# 去掉文件中每行文字换行，sanguo_utf8.txt是创建在代码路径下文章txt文档
f3 = open('sanguo_utf8.txt',encoding='utf-8')
print(f3.read().replace('\n',''))

上面功能用函数实现代码

def func(filename):
    print(open(filename,encoding='utf-8').read())
    print('test func')

func('name.txt')

用函数实现统计人物和武器出现次数例子

import re

def find_main_charecters(charecter_name):
    with open('sanguo_utf8.txt', encoding='utf-8') as f:
        data = f.read().replace("\n", "")
        name_num = re.findall(charecter_name, data)
        # print('主角 %s 出现了%s 次'%(charecter_name,len(name_num)))
    return charecter_name, len(name_num)


name_dict = {}
with open('name.txt', encoding='utf-8') as f:
    for line in f:
        names = line.split('|')
        for n in names:
            char_name, char_number = find_main_charecters(n)
            name_dict[char_name] = char_number

weapon_dict = {}
with open('weapon.txt', encoding='utf-8') as f:
        i = 1
        for line in f:
             if i%2 == 1:
                weapon_name, weapon_number = find_main_charecters(line.strip())
                weapon_dict[weapon_name] = weapon_number
             i = i+1


name_sorted = sorted(name_dict.items(), key=lambda item: item[1], reverse=True)
print(name_sorted[0:10])

weapon_sorted = sorted(weapon_dict.items(), key=lambda item: item[1], reverse=True)
print(weapon_sorted[0:10])

函数可变长参数例子

# #取得参数的个数
def  howlong(first, *other):
    print( 1 + len(other))

howlong(55,66,77)

函数迭代器、生成器

# iter() next()

list1 =[1, 2, 3]
it = iter(list1)
print( next(it))
print( next(it))
print( next(it))
print( next(it)) # except:StopIteration

#yield
def frange(start, stop, step):
    x = start
    while x < stop:
        yield x
        x += step

for i in frange(10,20,0.5):
    print(i)

Lambda表达式

def true():return True
lambda : True

def add(x,y): return x+y
add2 = lambda x,y : x+y
print(add2(5,6))

def testfunc(a_num): def testfunc(a_num):return a_num +1
var = lambda b_num : b_num + 1 
print(var(5))