python 编写常量板块

import sys class _CONSTANT: class ConstantError(TypeError) : pass def __setattr__(self, key, value): if key in self.__dict__.keys(): raise(self.ConstantError, "常量重新赋值错误!") self.__dict__[key] = value sys.modules[__name__] = _CONSTANT() #使用以下方式调用CONSTANT这个“常量”： CONSTANT = _CONSTANT() CONSTANT.TEST = 'test' print(CONSTANT.TEST) CONSTANT.TEST = 'test111' print(CONSTANT.TEST)

使用更高精度（超过17位小数）

from decimal import * print(getcontext()) getcontext().prec = 50 print(Decimal(1)/Decimal(9)) print(Decimal(1)/Decimal(19)) print(float(Decimal(1)/Decimal(19)))

 四舍五入

##.5时取相邻的偶数 round(1.5) #2 round(2.5) #2 rount(2.675) #3 ## ##5左侧是奇数舍去，偶数向上取整 round(2.635, 2) #2.63 round(2.645, 2) #2.65 round(2.655, 2) #2.65 round(2.665, 2) #2.67 round(2.675, 2) #2.67 ## ## ceil向上取整，floor向下取整 from math import ceil, floor round(2.5) #2 ceil(2.5) #3 floor(2.5) #2 round(2.3) #2 ceil(2.3) #3 floor(2.3) #2

 用complex创建复数

print(complex(1)) # 只有实部1 print(complex(1, 2)) # 实部为1，虚部为2 print(complex('1+2j')) # 实部为1，虚部为2

 迭代器

l = [1, 2, 3] iterName=iter(l) print(iterName) print(next(iterName)) print(next(iterName)) print(next(iterName)) print(next(iterName))

数据清洗

import pandas as pd #检查是否有重复数据 data=pd.read_csv('201711-2.csv', encoding='gbk') for isDuplicate in data.duplicated(): if isDuplicate==True: print(isDuplicate) #检查空值 data.isnull() #填充空值 data['IDNumber']=data['IDNumber'].fillna('123') #去除左右两边的空格 data['CardNo']=data['CardNo'].map(str.strip) #英文大小写转换 data['CardNo']=data['CardNo'].map(str.lower) data['CardNo']=data['CardNo'].map(str.title)#首字母大写 data['CardNo']=data['CardNo'].map(str.upper) #将日期型数据改成日期格式 data['CreateDateTime']=data['CreateDateTime'].fillna(time.strftime('%Y-%m-%d %H:%M:%S',time.localtime(time.time()))) data['CreateDateTime']=pd.to_datetime(data['CreateDateTime']) #保存 data.to_csv('201711-2Clear.csv', encoding='gbk')

 

来源：《python 数据分析与可视化》