PyDLR34

Februar 2020

Basemap (Beispiel aus dem Buch von Jake VanderPlas, Python Data Science Handbook https://jakevdp.github.io/PythonDataScienceHandbook/04.13-geographic-data-with-basemap.html)

# Die folgenden Links enthalten Hinweise zum auftretenden Fehler
# https://github.com/matplotlib/basemap/issues/420
# https://github.com/conda-forge/basemap-feedstock/issues/30
# https://github.com/conda-forge/basemap-feedstock/issues/45

import numpy as np
import matplotlib.pyplot as plt
from mpl_toolkits.basemap import Basemap

plt.figure(figsize=(8, 8))
m = Basemap(projection='ortho', resolution=None, lat_0=50, lon_0=-100)
m.bluemarble(scale=0.5);

Basemap installieren mit (basemap Version 1.2.0):

conda create -n basemap_test python=3.7.6  proj4=5.2.0 basemap pillow

In Spyder sieht man in der grafischen IPython Shell dann die Erdkugel. Das Problem liegt in höheren Versionen von proj4. Wenn man die Version von proj4 nicht explizit angibt, wird die Version 6.0.0 (oder ähnlich) verwendet. Mit dieser Version gibt es eine Fehlermeldung.

Andere 3D-Welten ausser Basemap:

• webglearth.com, examples.webglearth.com
• saredu.dlr.de/webGLobe
• saredu.dlr.de/webGLobe2
• github.com/webglearth/webglearth2
• https://automating-gis-processes.github.io/2016/Lesson5-World-3D.html (folium)

PyDLR33

Oktober 2019

• Eric Matthes, Python Crash Course, 2nd edition, 2019, Cheat Sheets https://ehmatthes.github.io/pcc_2e/

• f-string, multiline (https://realpython.com/python-f-strings)

  name = "Bob"
  profession = "baker"
  affiliation = "London"
  
  message = (
     f"Hi {name}. "
     f"You are a {profession}. "
     f"You were in {affiliation}."
  )
  
  print(message)

• Verschiedene Möglichkeiten, um Mehrzeilenstrings zu schreiben: https://www.techbeamers.com/python-multiline-string/

PyDLR32

Juli 2019

• Python - die Alternative zu Matlab? http://num.math.uni-goettingen.de/~schulz/data/python_talk.pdf

• Glumpy is a python library for scientific visualization that is both fast, scalable and beautiful. Glumpy offers an intuitive interface between numpy and modern OpenGL.

  http://glumpy.github.io

  Python & OpenGL for Scientific Visualization, Copyright (c) 2018 Nicolas P. Rougier, License: Creative Commons Attribution 4.0 International (CC BY-NC-SA 4.0), Website: http://www.labri.fr/perso/nrougier/python-opengl

  http://www.labri.fr/perso/nrougier/python-opengl/

• https://github.com/rougier/matplotlib-tutorial

• Python 4 Everybody by Charles Severance, https://www.py4e.com (free book)

PyDLR31

April 2019

# UnboundLocalError: local variable 'D' referenced before assignment
# Python Introductory Course 8.-10. April 2019
# Python 3.7

D = {}

def foo():
    if False:
        D = {}
    D["blue"] = "blau"
    print("D local:", D)
    return D


D = foo()
print(D)


# shorter:
# 1. Line '*' commented out: NameError: name 'D' is not defined
# 2. With line '*': UnboundLocalError: local variable 'D' referenced before assignment
# 3. With 'if True': works
def g():
    if False:
        D = {}  # (*)
    print(D)

g()

Explanation:

• https://docs.python.org/3/faq/programming.html#why-am-i-getting-an-unboundlocalerror-when-the-variable-has-a-value
• https://eli.thegreenplace.net/2011/05/15/understanding-unboundlocalerror-in-python

PyDLR23

Switch/Case with Python

def a():
    print("'a' was called")

def b():
    print("'b' was called")

def c():
    print("'c' was called")


D = { 'a' : a, 'b' : b, 'c' : c}

while True:
    s = input("your choice: ")
    if s in D:
        D[s]()
    else:
        break

PyDLR22