Python programming

• The end of a row is marked by a line break. If you want a statement to span several rows (for example, because otherwise the code will be very long and unreadable), you can insert a backslash \ at the end of the row. The line break will not be interpreted as such.
• A block is formed by indenting. All equally indented rows belong to the same block.
• Python is case-sensitive, which means that case-sensitive.

help(vtcapp)

help(vtcapp.getwithsql)

In Python, blocks are formed by indentation. This means that all rows belonging to the same level must be indented equally (watch for tabs):

if x ==1:
    y = 2

If a block does not (yet) contain a code, a “pass” must be set as a wildcard.

if x == 1:
    pass

Variables

Variables can be assigned easily. The data type is automatically recognized by the assignment. Here, too, it is important to pay attention to the case.

bearb = vtcapp.currentlogin()

Difference between local and global variables:

• Local variables can only be used within the feature and must be passed as parameters for each use in a different feature.
• Global variables are initialized once and are available in the same script in each feature.

Global variables are declared outside of features. To use a global variable within a feature, it must be loaded with global:

leistung = argobject # globale Variable deklarieren

def WertExtAendern(betrag): 
    global leistung # globale Variable verwenden 
    leistung.xWertExt = betrag 

def BearbeiterSetzen(bearbeiter): 
    global leistung 
    leistung.bearbeiter = bearbeiter

https://docs.python.org/library/stdtypes.html#comparisons

There are three ways to define strings in Python:

• 'String’
• ”String”
• ”"”String”"”

The string must be closed with the same symbol with which it is opened. Triple strings (“"”) can span any number of rows (e.g. form definitions or , while single and double strings can span one row each:

In the string, the placeholders are defined with curly brackets and with the method .format() passed in a tuple:

"Hallo, mein Name ist {} und ich bin {} Jahre alt.".format("Tobias", 18)

This variant in Python is very neat, since all variables are specified at the end. The string is displayed in its entirety and is not separated by special characters like [+, &].

If you want to output multiple lines of text, for example an address, you can insert a line break with \n.

A string is treated like a list in Python. The individual symbols can be iterated.

empfaengerStr = '; '.join(empfaenger)

You can get all the available string functions with the command:

help(str)

If you want to pass a path in Python, you have to be careful because backslashes in Python are used to encode control characters in strings. For example, the path C:\Documentation\temporary documents\.. becomes C:\Documentation emporary documents\.. and is invalid because \t is interpreted as a tab character. There are two ways to solve this problem:

• Either double all backslashes, i.e. 'C:\\Documentation\\temporary documents\\...'. Of course, this can only be done by typing the path “by hand”.
• “raw string,” which does not interpret any control characters. To do this, simply put an r immediately before the path: path = r’C:\documentation\temporary documents\...'.

https://docs.python.org/library/stdtypes.html#string-methods

https://docs.python.org/library/stdtypes.html#string-formatting-operations

Depending on how a value is initialized, it receives a specific data type. For example, the initialization a = 5 is interpreted as an integer. If you want to initialize the number as a float, you must specify a = 5.0 instead.

For information about the different number formats, use the help function:

• help(int)
• help(float)

For an operation with integer values, the result is an integer value:

10 / 4 = 2 (integer value of 2.5)

The same operation with a float value gives the following result:

10.0 / 4 = 2.5

or

float(10) / 4 = 2.5

This means: If one of the values is a float, the result is always output as a float:

1.5 * 7 = 10.5

1.5 * 6 = 9.0 (float value of 9)

The number representation is formatted as follows:

• {:} – Formatting symbol
• 0 – Prefix is 0
• 6 – Length of number
• 2 – Quantity of decimal places
• f – Float

'{:06.2f}'.format(555.3)

Result: 555.30

https://docs.python.org/library/stdtypes.html#numeric-types-int-float-long-complex

There are 3 different collection types in Python.

while Len(liste)>0:
    print pop()

for eintrag in liste:
    print eintrag
    del eintrag

'abc'.index('c')

'Hallo, mein Name ist Hans und ich lerne Python.'.count(' ')

xrange returns a list of numbers used primarily in for loops.

xrange(from, to, [step])

Examples of number lists:

xrange(1,3)

• Result: [1,2]

xrange(0,10,2)

• Result: [0,2,4,6,8]

xrange(1,12,3)

• Result: [1,4,7,10]

https://docs.python.org/library/stdtypes.html#sequence-types-str-unicode-list-tuple-buffer-xrange

In Python, there is the if query, the for loop, and the while loop.

if <Abfrage>:
    <do>
elif <Abfrage>:
    <do>
else:
    <do>

zahlen = [1,2,3]
if 1 in zahlen:
    print '1 vorhanden.'
else:
    print 'nicht vorhanden.'

for <variable> in <liste>:
    <do>

The For loop in Python knows the beginning and end by indentation and therefore does not need a Next.

bearbeiter = vtcapp.currentlogin()
projektListe = bearbeiter.evalocl("eigProjekte->orderby(code)")
for projekt in projektListe:
    print projekt.code  # Members werden mit Punkt angesprochen.

for i in xrange(1,11):
    print str(i)  # Zahlen von 1-10

while <Abfrage>:
    <do>

i = 1
while i <= 10:
    print 'Die Zahl ist {}'.format(i)
    i += 1

In Python, features are started with the def keyword. The return value is returned with the return keyword. In Python, there is no distinction between feature and procedure. Both are called def. The feature returns something and the procedure does not.

def ChangeText(leist):
    leist.text = ...

After that, it can be accessed in the code:

ChangeText(argobject)

def produkt(a, b):
    return a*b

def getAktive(projektListe):
    resList = []
    for projekt in projektListe:
        if projekt.aktiv:
            resList.append(projekt)
    return resList

def erstelleAktivitaet(projekt):
    newAkt = vtcapp.createobject("Aktivitaet")
    newAkt.projekt = projekt
    newAkt.bearbeiter = projekt.projektleiter

    # Aktivitaet anzeigen
    vtcapp.showdetailform(newAkt)

def aktiveTrennen(projektListe):
    for projekt in projektListe:
        if projekt.aktiv:
            aktive.append(projekt)
        else:
            inaktive.append(projekt)
    return (aktive, inaktive) # Tuple of Lists

aktive, inaktive = aktiveTrennen(projektListe)

When calling a feature that does not expect any parameters, it is very important that the parentheses are not forgotten. Example:

vtcapp.currentlogin #Falsch, Funktion wird nicht aufgerufen, es wird eine Fehlermeldung ausgegeben
vtcapp.currentlogin() #Richtig