1.十进制转换为二进制
>>> bin(10) '0b1010'2.十进制转换为八进制
>>> oct(9) '0o11'3.十进制转换为十六进制
>>> hex(15) '0xf'4.字符串转换为字节类型
>>> s = "apple" >>> bytes(s,encoding='utf-8') b'apple'5.字符类型、数值型等转换为字符串类型
>>> i = 100 >>> str(i) '100'6.十进制整数对应的 ASCII 字符
>>> chr(65) 'A'7.ASCII字符对应的十进制数
>>> ord('A') 658.整数或数值型字符串转换为浮点数
>>> float(3) 3.09.创建数据字典的几种方法
>>> dict() {} >>> dict(a='a',b='b') {'a': 'a', 'b': 'b'} >>> dict(zip(['a','b'],[1,2])) {'a': 1, 'b': 2} >>> dict([('a',1),('b',2)]) {'a': 1, 'b': 2}10.排序函数
>>> a = [1,4,2,3,1] #降序 >>> sorted(a,reverse=True) [4, 3, 2, 1, 1] >>> a = [{'name':'xiaoming','age':18,'gender':'male'}, {'name':'xiaohong','age':20,'gender':'female'}] #按 age升序 >>> sorted(a,key=lambda x: x['age'],reverse=False) [{'name': 'xiaoming', 'age': 18, 'gender': 'male'}, {'name': 'xiaohong', 'age': 20, 'gender': 'female'}]11.求和函数
>>> a = [1,4,2,3,1] >>> sum(a) 11 #求和初始值为1 >>> sum(a,1) 1212.计算字符串型表达式的值
>>> s = "1 + 3 +5" >>> eval(s) 9 >>> eval('[1,3,5]*3') [1, 3, 5, 1, 3, 5, 1, 3, 5]13.获取用户输入内容
>>> input() I'm typing "I'm typing "14.print 用法
>>> lst = [1,3,5] # f 打印 >>> print(f'lst: {lst}') lst: [1, 3, 5] # format 打印 >>> print('lst:{}'.format(lst)) lst:[1, 3, 5]15.格式化字符串常见用法
>>> print("i am {0},age {1}".format("tom",18)) i am tom,age 18 >>> print("{:.2f}".format(3.1415926)) # 保留小数点后两位 3.14 >>> print("{:+.2f}".format(-1)) # 带符号保留小数点后两位 -1.00 >>> print("{:.0f}".format(2.718)) # 不带小数位 3 >>> print("{:0>3d}".format(5)) # 整数补零，填充左边, 宽度为3 005 >>> print("{:,}".format(10241024)) # 以逗号分隔的数字格式 10,241,024 >>> print("{:.2%}".format(0.718)) # 百分比格式 71.80% >>> print("{:.2e}".format(10241024)) # 指数记法 1.02e+07值（值得注意，自定义的实例都可哈希，list, dict, set等可变对象都不可哈希）
>>> class Student(): def __init__(self,id,name): self.id = id self.name = name >>> xiaoming = Student('001','xiaoming') >>> hash(xiaoming) -922337189423410468816.if not x
直接使用 x 和 not x 判断 x 是否为 None 或空
x = [1,3,5] if x: print('x is not empty ') if not x: print('x is empty')17.打开文件，并返回文件对象
>>> import os >>> os.chdir('D:/source/dataset') >>> os.listdir() ['drinksbycountry.csv', 'IMDB-Movie-Data.csv', 'movietweetings', 'titanic_eda_data.csv', 'titanic_train_data.csv'] >>> o = open('drinksbycountry.csv',mode='r',encoding='utf-8') >>> o.read() "country,beer_servings,spirit_servings,wine_servings,total_litres_of_pur e_alcohol,continent\nAfghanistan,0,0,0,0.0,Asia\nAlbania,89,132,54,4.9,"18. 创建迭代器
>>> class TestIter(): def __init__(self,lst): self.lst = lst # 重写可迭代协议__iter__ def __iter__(self): print('__iter__ is called') return iter(self.lst)迭代 TestIter 类：
>>> t = TestIter() >>> t = TestIter([1,3,5,7,9]) >>> for e in t: print(e) __iter__ is called 1 3 5 7 919.创建range迭代器
>>> t = range(11) >>> t = range(0,11,2) >>> for e in t: print(e) 0 2 4 6 8 1020.反向
>>> rev = reversed([1,4,2,3,1]) >>> for i in rev: print(i) 1 3 2 4 121.打包
>>> x = [3,2,1] >>> y = [4,5,6] >>> list(zip(y,x)) [(4, 3), (5, 2), (6, 1)] >>> for i,j in zip(y,x): print(i,j) 4 3 5 2 6 122.过滤器
函数通过 lambda 表达式设定过滤条件，保留 lambda 表达式为True的元素：
>>> fil = filter(lambda x: x>10,[1,11,2,45,7,6,13]) >>> for e in fil: print(e) 11 45 1323. split 分割**
>>> 'i love python'.split(' ') ['i', 'love', 'python']24. 提取后缀名
>>> import os >>> os.path.splitext('D:/source/dataset/new_file.txt') ('D:/source/dataset/new_file', '.txt') #[1]：后缀名25.斐波那契数列前n项
>>> def fibonacci(n): a, b = 1, 1 for _ in range(n): yield a a, b = b, a+b # 注意这种赋值 >>> for fib in fibonacci(10): print(fib) 1 1 2 3 5 8 13 21 34 5526.list 等分 n 组
>>> from math import ceil >>> def divide_iter(lst, n): if n <= 0: yield lst return i, div = 0, ceil(len(lst) / n) while i < n: yield lst[i * div: (i + 1) * div] i += 1 >>> for group in divide_iter([1,2,3,4,5],2): print(group) [1, 2, 3] [4, 5]27. 列表生成式
data = [1, 2, 3, 5, 8] result = [i * 2 for i in data if i & 1] # 奇数则乘以2 print(result) # [2, 6, 10]28.字典生成式
keys = ['a', 'b', 'c'] values = [1, 3, 5] d = {k: v for k, v in zip(keys, values)} print(d)29.判断字符串是否包含某个子串，使用in明显更加可读
x = 'zen_of_python' if 'zen' in x: print('zen is in')30.zip 打包
使用 zip 打包后结合 for 使用输出一对
keys = ['a', 'b', 'c'] values = [1, 3, 5] for k, v in zip(keys, values): print(k, v)