Archive for the ‘Python / SciPy / pandas’ Category.

Time in Python

A short summary on Python’s timestamps:

import datetime
 
now = datetime.datetime.now()
 
print(now.strftime('%Y-%m-%d %H:%M'))
print(now.isoformat())

From the module’s documentation:

Directive Meaning
%a Locale’s abbreviated weekday name.
%A Locale’s full weekday name.
%b Locale’s abbreviated month name.
%B Locale’s full month name.
%c Locale’s appropriate date and time
representation.
%d Day of the month as a decimal number [01,31].
%H Hour (24-hour clock) as a decimal number
[00,23].
%I Hour (12-hour clock) as a decimal number
[01,12].
%j Day of the year as a decimal number [001,366].
%m Month as a decimal number [01,12].
%M Minute as a decimal number [00,59].
%p Locale’s equivalent of either AM or PM.
%S Second as a decimal number [00,61].
%U Week number of the year (Sunday as the first
day of the week) as a decimal number [00,53].
All days in a new year preceding the first
Sunday are considered to be in week 0.
%w Weekday as a decimal number [0(Sunday),6].
%W Week number of the year (Monday as the first
day of the week) as a decimal number [00,53].
All days in a new year preceding the first
Monday are considered to be in week 0.
%x Locale’s appropriate date representation.
%X Locale’s appropriate time representation.
%y Year without century as a decimal number
[00,99].
%Y Year with century as a decimal number.
%z Time zone offset indicating a positive or
negative time difference from UTC/GMT of the
form +HHMM or -HHMM, where H represents decimal
hour digits and M represents decimal minute
digits [-23:59, +23:59].
%Z Time zone name (no characters if no time zone
exists).
%% A literal '%' character.

Uwe

Uwe Ziegenhagen likes LaTeX and Python, sometimes even combined. Do you like my content and would like to thank me for it? Consider making a small donation to my local fablab, the Dingfabrik Köln. Details on how to donate can be found here Spenden für die Dingfabrik.

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Slides from my 2016 Froscon Presentation „Using Python for Scientific Research“

Here are my slides from the Froscon 2016 presentation „Using Python for Scientific Research“.

Slides: Froscon_Slides_2016

Video: Video Recording (The screen was flickering most of the time, pretty annoying and distracting)

I will continously update and expand this presentation during the next months, if you want to receive updates follow the GitHub repository: https://github.com/UweZiegenhagen/2016-Python-Data-Analysis-Slides/

Uwe

Uwe Ziegenhagen likes LaTeX and Python, sometimes even combined. Do you like my content and would like to thank me for it? Consider making a small donation to my local fablab, the Dingfabrik Köln. Details on how to donate can be found here Spenden für die Dingfabrik.

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Parsing Emacs Orgmode files with Python

Here’s some experimental (alpha) code to parse Emacs Orgmode files. It’s far from complete, I only aim at parsing basic TODO strings with level (**), status (TODO, DONE), priority (#A, #B, #C), task and tags.

2016-09-03: It takes my actual orgmode file, so it’s working fine.

2016-09-04: I created a github repo, code updates will be added there, only: https://github.com/UweZiegenhagen/python-orgmode-parser

# -*- coding: utf-8 -*-
import re
 
def parseEmaceOrgmode(s):
    r = '^([\*]+)?\s?(TODO|PROGRESSING|FEEDBACK|VERIFY|POSTPONED|DELEGATED|CANCELLED|DONE)?\s?(\[#[A|B|C]\])?\s?(.*?)\s*(:(.*):)?$'    
    m = re.search(r,s)
    level = m.group(1)
    if (level is not None):
        level = len(level)
    prio = m.group(3)
    if (prio is not None):
        prio = prio[2:3]
    tags = []
    a = m.group(5)
    if a != None:
        b = len(a)-1
        a= a[1:b]
        a = a.split(':')
    tags.append(a)
    return(level, m.group(2), prio, m.group(4), tags)
 
with open("../orgmode.org", "r") as ins:
    for line in ins:
        level, status, priority, task, tags = parseEmaceOrgmode(line)
        if level is not None:        
            print('Level:', level)
            print('Status:', status)
            print('Priority:', priority)
            print('Task:', task)
            print('Tags:',tags,'\n\n')

Uwe

Uwe Ziegenhagen likes LaTeX and Python, sometimes even combined. Do you like my content and would like to thank me for it? Consider making a small donation to my local fablab, the Dingfabrik Köln. Details on how to donate can be found here Spenden für die Dingfabrik.

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Ein einfaches Python-Beispiel für Klassen und Funktionen

Hier noch ein einfaches Python-Beispiel für Klassen und Funktionen, das ich vor ein paar Tagen geschrieben habe. Die Punkt-Klasse erhält eine entsprechende Funktion, um die Euklidische Distanz zu einem anderen Punkt zu bestimmen.

# -*- coding: utf-8 -*-
import math as m
 
class Point:
 
    def __init__(self,x,y):
        self.x = x
        self.y = y
 
    def calcEuclidDistanceToPoint(self,x,y):
        return m.sqrt(m.pow(self.x-x,2) + m.pow(self.y-y,2))
 
p1 = Point(0,0)
p2 = Point(1,1)
print(p2.calcEuclidDistanceToPoint(p1.x,p1.y))
runfile('euclidDistance.py', wdir='E:/Python')
1.4142135623730951

Uwe

Uwe Ziegenhagen likes LaTeX and Python, sometimes even combined. Do you like my content and would like to thank me for it? Consider making a small donation to my local fablab, the Dingfabrik Köln. Details on how to donate can be found here Spenden für die Dingfabrik.

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Lineare Gleichungen lösen mit numpy

Hier ein kurzes Beispiel aus der numpy-Dokumentation, wie man mit Hilfe von numpy lineare Gleichungssysteme lösen kann:

Zu lösen sind folgende Gleichungen:

  • 3 * x0 + 1 * x1 = 9
  • 1 * x0 + 2 * x1 = 8

Die Koeffizienten kommen in die entsprechenden numpy-Arrays, dann ruft man linalg.solve auf:

import numpy as np
 
a = np.array([[3,1], [1,2]])
b = np.array([9,8])
x = np.linalg.solve(a, b)
print(x) # gibt [ 2.  3.]

pff

Den Plot habe ich mit LaTeX erstellt, siehe http://uweziegenhagen.de/?p=3516.

Uwe

Uwe Ziegenhagen likes LaTeX and Python, sometimes even combined. Do you like my content and would like to thank me for it? Consider making a small donation to my local fablab, the Dingfabrik Köln. Details on how to donate can be found here Spenden für die Dingfabrik.

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Parallel LaTeXing with Python Threads

Based on an example from stackexchange I have created a small example on parallel TeX compilation.

# -*- coding: utf-8 -*-
"""
Created on 2016-07-06
Uwe Ziegenhagen
based on http://stackoverflow.com/questions/16181121/python-very-simple-multithreading-parallel-url-fetching-without-queue
"""
 
from multiprocessing.pool import ThreadPool
from time import time as timer
import os
 
files = ['test-01.tex','test-02.tex','test-03.tex','test-04.tex','test-05.tex',
'test-06.tex','test-07.tex','test-08.tex','test-09.tex','test-10.tex']
 
def compile_file(cfile):
	try:
		result = os.system('pdflatex -interaction=batchmode ' + cfile)
		return cfile, None
	except Exception as e:
		return cfile, e	
 
start = timer()
results = ThreadPool(8).imap_unordered(compile_file, files)
for cfile, error in results:
	if error is None:
		print("%r compiled in %ss" % (cfile, timer() - start))
	else:
		print("Error compiling %r: %s" % (cfile, error))
		print("Elapsed Time: %s" % (timer() - start,))
 
print('Gesamtzeit',timer() - start)

Uwe

Uwe Ziegenhagen likes LaTeX and Python, sometimes even combined. Do you like my content and would like to thank me for it? Consider making a small donation to my local fablab, the Dingfabrik Köln. Details on how to donate can be found here Spenden für die Dingfabrik.

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Spalte aus Text-Datei extrahieren mit Python

Hier ein Quick & Dirty Code, um eine Spalte aus einer Text-Datei zu extrahieren. Geht auch mit AWK, aber wenn man nur Python hat…

def splitFileOneColumn(inputFile,outputFile,columnSeparator,column):
    with open(inputFile, 'r') as infile:
        with open(outputFile, 'w') as outfile:
            for line in infile:
                s = line.split(columnSeparator)
                outfile.write(s[column]+os.linesep) # '\r\n' on Windows, '\n' on Unix/Linux/Mac
            outfile.close()
    infile.close()

Bei Gelegenheit muss ich das mal um die Möglichkeit erweitern, n Spalten zu extrahieren.

Uwe

Uwe Ziegenhagen likes LaTeX and Python, sometimes even combined. Do you like my content and would like to thank me for it? Consider making a small donation to my local fablab, the Dingfabrik Köln. Details on how to donate can be found here Spenden für die Dingfabrik.

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Daten aggregieren mit pandas

I recently came across a „challenge“ where I needed to combine various rows. Each row was identified by Key1 and Key2 and had two interesting columns, Foo and Bar. For each Key1 there may be a few Key2, for each Key2 n Foo/Bar entries. While all Foos are distinct per Key1 and Key2 the Bar column may appear j times.

The goal was to get a list of unique Bar items for each Key1/Key2 combination.

Key1 Key2 Foo Bar
0 C1 T1 a1 rc-1
1 C1 T1 a2 rc-1
2 C1 T1 a3 rc-1
3 C1 T1 a4 rc-1
4 C2 T2 b1 rc-1
5 C2 T2 b2 rc-2
6 C3 T3 c1 rc-3
7 C4 T4 d1 rc-4
8 C4 T4 d2 rc-5
9 C4 T4 d3 rc-4

The following Python code nicely did the job, thanks to http://stackoverflow.com/questions/17841149/pandas-groupby-how-to-get-a-union-of-strings

# -*- coding: utf-8 -*-
import pandas as pd
 
def unique(liste):
    """ takes a list of elements, separated by comma and returns sorted string of unique items separated by comma """
    a = liste.split(',')
    b = sorted(set(a))
    return ','.join(b)
 
df = pd.read_excel('groupb_Beispiel.xlsx')
print(df)
 
grouped = df.groupby(['Key1','Key2'],as_index=False)['Bar'].agg(lambda col: ','.join(col))
grouped = pd.DataFrame(grouped)
 
grouped['Unique'] = grouped['Bar'].apply(unique)
 
print(grouped)
 
grouped.to_excel('result.xlsx')
Key1 Key2 Bar Unique
0 C1 T1 rc-1,rc-1,rc-1,rc-1 rc-1
1 C2 T2 rc-1,rc-2 rc-1,rc-2
2 C3 T3 rc-3 rc-3
3 C4 T4 rc-4,rc-5,rc-4 rc-4,rc-5

Uwe

Uwe Ziegenhagen likes LaTeX and Python, sometimes even combined. Do you like my content and would like to thank me for it? Consider making a small donation to my local fablab, the Dingfabrik Köln. Details on how to donate can be found here Spenden für die Dingfabrik.

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Folien zum Data Science Meetup vom 29.01.2016

Hier meine Folien zum Data Science Meetup vom 29.01.2016.

Pandas (PDF)

Uwe

Uwe Ziegenhagen likes LaTeX and Python, sometimes even combined. Do you like my content and would like to thank me for it? Consider making a small donation to my local fablab, the Dingfabrik Köln. Details on how to donate can be found here Spenden für die Dingfabrik.

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Zeilen kombinieren mit pandas

Vor einiger Zeit hatte ich eine Excel-Datei zu bearbeiten, in der in einer Spalte die Spaltennamen, in einer anderen die korrespondieren Werte standen. Immer drei Zeilen bildeten den eigentlichen Datensatz. Mit wenigen Zeilen Pandas und cleverer Adressierung der Ergebnis-Zelle.

Spaltenname Wert
ColA Andi
ColB Berni
ColC Cesar
ColA Dorian
ColB Ernest
ColC Frank

 

import pandas as pd
 
# Lade die Daten
daten = pd.read_excel('combine.xlsx')
# Erstelle leeren Dataframe mit den Spaltennamen aus den Excelzeilen 
verarbeitet = pd.DataFrame(columns=['ColA','ColB','ColC'])
 
# Iteriere über die Daten
for i, row in daten.iterrows():
    # ganzzahliges Teilen, um die Zeile zu bestimmen
    # in die die Zelle gehört, Spalte ergibt sich aus dem Wert in 'Spalte'
    verarbeitet.loc[i // 3,row['Spalte']] = row['Wert']
 
print(verarbeitet)
ColA ColB ColC
0 Andi Berni Cesar
1 Dorian Ernest Frank

Nachtrag: Stephan vom Kölner Data Science Meetup hat mir noch einen alternativen Weg gezeigt:

import pandas as pd
 
data = {'A': ["cola", "colb", "colc", "cola", "colb", "colc"], "B": [1, 2, 3, 4, 5, 6]}
data = pd.DataFrame(data)
gb = data.groupby('A')
res = pd.DataFrame()
for key in gb.groups:
    res[key] = gb.get_group(key)['B'].values.flatten()
 
print(res)

Uwe

Uwe Ziegenhagen likes LaTeX and Python, sometimes even combined. Do you like my content and would like to thank me for it? Consider making a small donation to my local fablab, the Dingfabrik Köln. Details on how to donate can be found here Spenden für die Dingfabrik.

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