python常用技巧 — 杂

目录：

1. 找到字符串中的所有数字（python find digits in string）

2. python 生成连续的浮点数（如 0.1， 0.2， 0.3， 0.4， ... , 0.9）（python range() for floats）

3. 判断两个矩形重叠程度 (python calculate overlap of two rectangle)

4. python 画多边形 (python draw polygon)

5. python 条件语句用一行实现 （python condition statement on one row）

内容：

1. 找到字符串中的所有数字（python find digits in string）

方法1：

https://stackoverflow.com/questions/12005558/python-find-digits-in-a-string

name = 'body_flaw_validate_set20191119170917_'
list(filter(str.isdigit, name))
['2', '0', '1', '9', '1', '1', '1', '9', '1', '7', '0', '9', '1', '7']

方法2：

https://www.geeksforgeeks.org/python-extract-digits-from-given-string/

import re
name = 'body_flaw_validate_set20191119170917_'
re.sub("\D", "", name)
'20191119170917'

2. python 生成连续的浮点数（如 0.1， 0.2， 0.3， 0.4， ... , 0.9）python range() for floats

https://stackoverflow.com/questions/7267226/range-for-floats

方法1：

[x / 10.0 for x in range(1, 10)]
[0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9]

方法2:

import pylab as pl
pl.frange(0.1,0.9,0.1)
array([0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9])

方法3：

import numpy
numpy.linspace(0.1, 0.9, num=9)
array([0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9])

3. 判断两个矩形重叠程度 (python calculate overlap of two rectangle)

https://stackoverflow.com/questions/27152904/calculate-overlapped-area-between-two-rectangles

更加详细的例子：

https://shapely.readthedocs.io/en/stable/manual.html

from shapely.geometry import Polygon
polygon = Polygon([(3, 3), (5, 3), (5, 5), (3, 5)])
other_polygon = Polygon([(1, 1), (4, 1), (4, 3.5), (1, 3.5)])
intersection = polygon.intersection(other_polygon)
print(intersection.area)
# 0.5

4. python 画多边形 (python draw polygon)

https://www.life2coding.com/draw-polygon-on-image-using-python-opencv/

 import numpy as np
 import cv2

 img = np.zeros((512, 512, 3), dtype = "uint8")

 penta = np.array([[[40,160],[120,100],[200,160],[160,240],[80,240]]], np.int32)
 triangle = np.array([[[240, 130], [380, 230], [190, 280]]], np.int32)
 cv2.polylines(img, [triangle], True, (0,255,0), thickness=3)

 img_mod = cv2.polylines(img, [penta], True, (255,120,255),3)

 cv2.imshow('Shapes', img_mod)

 cv2.waitKey(0)
 cv2.destroyAllWindows()

5. python 条件语句用一行实现 （python condition statement on one row）

https://stackoverflow.com/questions/2802726/putting-a-simple-if-then-else-statement-on-one-line

// 格式
value_when_true if condition else value_when_false
// 例子
'Yes' if fruit == 'Apple' else 'No'

6.