标签：apple name gif int pre lis asd hello gen
列表表达式：
程序一：
常规写法：
L = [] for x in range(1, 11): L.append(x * x) print(L) #[1, 4, 9, 16, 25, 36, 49, 64, 81, 100]
列表生成式写法：
L = [x * x for x in range(1, 11)] #[1, 4, 9, 16, 25, 36, 49, 64, 81, 100] #写列表生成式时，把要生成的元素x * x放到前面，后面跟for循环，就可以把list创建出来，十分有用，多写几次，很快就可以熟悉这种语法。for循环后面还可以加上if判断，这样我们就可以筛选出仅偶数的平方： L1 = [x * x for x in range(1, 11) if x % 2 == 0] print(L1) #[4, 16, 36, 64, 100]
程序二：
常规写法：
list = [1,2,3,4] s = ‘hello‘ list1 = [] for num in list: for s1 in s: t=(num,s1) list1.append(t) print(list1) #[(1, ‘h‘), (1, ‘e‘), (1, ‘l‘), (1, ‘l‘), (1, ‘o‘), (2, ‘h‘), (2, ‘e‘), (2, ‘l‘), (2, ‘l‘), (2, ‘o‘), (3, ‘h‘), (3, ‘e‘), (3, ‘l‘), (3, ‘l‘), (3, ‘o‘), (4, ‘h‘), (4, ‘e‘), (4, ‘l‘), (4, ‘l‘), (4, ‘o‘)]
列表生成式写法：
list1 = [(num,s1) for num in list for s1 in s] print(list1) #[(1, ‘h‘), (1, ‘e‘), (1, ‘l‘), (1, ‘l‘), (1, ‘o‘), (2, ‘h‘), (2, ‘e‘), (2, ‘l‘), (2, ‘l‘), (2, ‘o‘), (3, ‘h‘), (3, ‘e‘), (3, ‘l‘), (3, ‘l‘), (3, ‘o‘), (4, ‘h‘), (4, ‘e‘), (4, ‘l‘), (4, ‘l‘), (4, ‘o‘)]
程序三：
常规写法：
import os # 查看test文件夹所有的绝对路径 g = os.walk(r‘E:\test‘) file_path_list = [] for i in g: print(i) for j in i[-1]: file_path_list.append(‘%s\\%s‘ % (i[0], j)) print(‘%s\\%s‘ % (i[0], j)) print(file_path_list)
列表生成式写法：
g = os.walk(r‘E:\test‘) file_path_list = [‘%s\\%s‘ % (i[0], j) for i in g for j in i[-1]] print(file_path_list)
生成器表达式：
相比列表表达式，只不过将[]换成了()，更加省内存。
程序一：
列表生成式写法：
L = [x * x for x in range(1, 11)] #[1, 4, 9, 16, 25, 36, 49, 64, 81, 100] #写列表生成式时，把要生成的元素x * x放到前面，后面跟for循环，就可以把list创建出来，十分有用，多写几次，很快就可以熟悉这种语法。for循环后面还可以加上if判断，这样我们就可以筛选出仅偶数的平方： L1 = [x * x for x in range(1, 11) if x % 2 == 0] print(L1) #[4, 16, 36, 64, 100]
生成器表达式写法：
L11 = (x * x for x in range(1, 11)) print(L11) print(next(L11)) print(next(L11)) print(next(L11)) for L in L11: print(L11) L12 = (x * x for x in range(1, 11) if x % 2 == 0) print(L12) print(next(L12)) print(next(L12)) print(next(L12)) for L in L12: print(L12)
程序二：
常规写法：
f=open(‘a.txt‘) l=[]<br>f.seek(0) #光标移动到文档首行首位 for line in f: line=line.strip() l.append(line)
列表表达式写法：
f=open(‘a.txt‘) f.seek(0) l1=[line.strip() for line in f] print(l1)
生成器表达式写法：
f=open(‘a.txt‘) f.seek(0) g=(line.strip() for line in f) print(g) print(next(g))
程序三：
生成器表达式写法：
f=open(‘a.txt‘) g=(line.strip() for line in f) #g为迭代器 l=list(g) #list(可迭代对象)，迭代取出g中的所有内容 print(l) #[‘asdfasdfasdfasdfasdf‘, ‘123123123123‘, ‘123123123123‘, ‘123123123123‘, ‘123123123123‘, ‘123123123123‘, ‘123123123123‘, ‘123123123123‘, ‘123123123123‘, ‘123123123123‘, ‘123123123123‘, ‘123123123123‘, ‘123123123123‘, ‘123123123123‘, ‘123123123123‘, ‘123123123123‘, ‘123123123123‘, ‘123123123123‘, ‘123123123123‘, ‘123123123123‘, ‘123123123123‘, ‘‘, ‘asdfasdfasdfasdf‘] nums_g=(i for i in range(3)) # print(sum([1,2,3,4])) print(sum(nums_g)) #sum(可迭代对象)，迭代将g中的所有元素相加
asdfasdfasdfasdfasdf 123123123123 123123123123 123123123123 123123123123 123123123123 123123123123 123123123123 123123123123 123123123123 123123123123 123123123123 123123123123 123123123123 123123123123 123123123123 123123123123 123123123123 123123123123 123123123123 123123123123 asdfasdfasdfasdf
程序四：
常规方法：
money_l=[] with open(‘b.txt‘) as f: for line in f: goods=line.split() res=float(goods[-1])*float(goods[-2]) money_l.append(res) print(money_l) #[30.0, 1000000.0, 6000.0, 90000.0, 30.0]
生成器表达式写法：
f=open(‘b.txt‘) g=(float(line.split()[-1])*float(line.split()[-2]) for line in f) print(sum(g)) #1096060.0
程序五：
常规方法：
res=[] with open(‘b.txt‘) as f: for line in f: # print(line) l=line.split() # print(l) d={} d[‘name‘]=l[0] d[‘price‘]=l[1] d[‘count‘]=l[2] res.append(d) print(res) #[{‘name‘: ‘apple‘, ‘price‘: ‘10‘, ‘count‘: ‘3‘}, {‘name‘: ‘tesla‘, ‘price‘: ‘1000000‘, ‘count‘: ‘1‘}, {‘name‘: ‘mac‘, ‘price‘: ‘3000‘, ‘count‘: ‘2‘}, {‘name‘: ‘lenovo‘, ‘price‘: ‘30000‘, ‘count‘: ‘3‘}, {‘name‘: ‘chicken‘, ‘price‘: ‘10‘, ‘count‘: ‘3‘}]
生成器表达式写法：
with open(‘b.txt‘) as f: res=(line.split() for line in f) print(res) dic_g=({‘name‘:i[0],‘price‘:i[1],‘count‘:i[2]} for i in res) print(dic_g) apple_dic=next(dic_g) print(apple_dic[‘count‘]) apple_dict=next(dic_g) print(apple_dict) #{‘name‘: ‘tesla‘, ‘price‘: ‘1000000‘, ‘count‘: ‘1‘}
apple 10 3 tesla 1000000 1 mac 3000 2 lenovo 30000 3 chicken 10 3
#取出单价>10000 with open(‘b.txt‘) as f: res=(line.split() for line in f) # print(res) dic_g=({‘name‘:i[0],‘price‘:i[1],‘count‘:i[2]} for i in res if float(i[1]) > 10000) print(dic_g) #<generator object <genexpr> at 0x0000000001E05888> print(list(dic_g)) #[{‘name‘: ‘tesla‘, ‘price‘: ‘1000000‘, ‘count‘: ‘1‘}, {‘name‘: ‘lenovo‘, ‘price‘: ‘30000‘, ‘count‘: ‘3‘}]
标签：apple name gif int pre lis asd hello gen
原文地址：https://www.cnblogs.com/xiaodai0/p/10163108.html
