lhsfcboy

"""最小公倍数与最大公约数"""

def gcd(*numbers):
    """Return the greatest common divisor of the given integers"""
    from fractions import gcd
    return reduce(gcd, numbers)

def lcm(*numbers):
    """Return lowest common multiple."""    
    def lcm(a, b):

lhsfcboy

#!pip install functools 
from functools import partial
import numpy
from matplotlib import pyplot

# Define a PDF
x_samples = numpy.arange(-3, 3.01, 0.01)
PDF = numpy.empty(x_samples.shape)
PDF[x_samples < 0] = numpy.round(x_samples[x_samples < 0] + 3.5) / 3
PDF[x_samples >= 0] = 0.5 * numpy.cos(numpy.pi * x_samples[x_samples >= 0]) + 0.5

lhsfcboy

"""Python并没有switch-case的语法，等效的用法要么是像上面一样用if-elif-else的组合，要么可以考虑字典"""

pets = ['dog', 'cat', 'droid', 'fly']
food_for_pet = {
    'dog': 'steak', 
    'cat': 'milk', 
    'droid': 'oil', 
    'fly': 'sh*t'
}

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moves = ['up', 'left', 'down', 'right']

def move_up(x):         # 定义向上的操作
    x[1] += 1

def move_down(x):       # 定义向下的操作
    x[1] -= 1

def move_left(x):       # 定义向左的操作
    x[0] -= 1

lhsfcboy

"""对于filter和map，在Python2中返回结果是列表，Python3中是生成器"""

import functools

map(lambda x: x**2, [1, 2, 3, 4])                     # [1, 4, 9, 16]
map(lambda x, y: x + y, [1, 2, 3], [5, 6, 7])         # [6, 8, 10]

functools.reduce(lambda x, y: x + y, [1, 2, 3, 4])    # ((1+2)+3)+4=10

filter(lambda x: x % 2, [1, 2, 3, 4, 5])              # 筛选奇数，[1, 3, 5]

lhsfcboy

a = 'Life is short, you need Python'
a.lower()              	# 'life is short, you need Python'
a.upper()               	# 'LIFE IS SHORT, YOU NEED PYTHON'
a.count('i')            	# 2
a.find('e')             	# 从左向右查找'e'，3
a.rfind('need')         	# 从右向左查找'need'，19
a.replace('you', 'I')   # 'Life is short, I need Python'
tokens = a.split()    	# ['Life', 'is', 'short,', 'you', 'need', 'Python']
b = ' '.join(tokens)	# 用指定分隔符按顺序把字符串列表组合成新字符串
c = a + '\n'            	# 加了换行符，注意+用法是字符串作为序列的用法

lhsfcboy

a = 'I’m like a {} chasing {}.'
# 按顺序格式化字符串，'I’m like a dog chasing cars.'
a.format('dog', 'cars')

# 在大括号中指定参数所在位置
b = 'I prefer {1} {0} to {2} {0}'
b.format('food', 'Chinese', 'American')

# >代表右对齐，>前是要填充的字符，依次输出：
# 000001

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with open('name_age.txt', 'r') as fread, open('age_name.txt', 'w') as fwrite:
    line = fread.readline()
    while line:
        name, age = line.rstrip().split(',')
        fwrite.write('{},{}\n'.format(age, name))
        line = fread.readline()

lhsfcboy

for filepath in filelist:   # filelist中是文件路径的列表
    try:
        with open(filepath, 'r') as f:
            # 执行数据处理的相关工作
            pass
        
        print('{} is processed!'.format(filepath))
    except IOError:
        print('{} with IOError!'.format(filepath))
        # 异常的相应处理

lhsfcboy

Target:
        1、第1章 第1节 集合（1）2、第1章 第1节 集合（2）3、第1章 第1节 集合
Purpose:
        Search for "1、" and replace with newline plus that
Solution:
        Search:    (\d{1,3}\、)
        Replace:   \n\1
-----------------------------------------------------------------------
Target:
        第14章 第2节 第二类曲线积分与第二类曲面积分