Python - Working With Strings

Basics

Special Characters

String Prefixes

Getting the String Length

Concatenating Strings

Comparing Strings

Accessing an Individual Character of a String

Searching for Characters and Substrings

Getting a Substring

Splitting Strings

Removing Extra Spaces From a String

Replacing Characters and Substrings

Changing the Letter Case

Working With String Lists

A string is a sequence of symbols or digits. Strings are among the most frequently used data types. Like any other data types, strings in TestComplete are represented as OLE-compatible variants.

In Python, a sequence of literal characters enclosed in a matching pair of quotation marks is recognized as a string. Quotation marks can be single ('), double (") or triple quotes (""" or '''). The quotation characters are allowed within a string if they do not match the enclosing pair. All the strings below are valid:

To deal with strings, TestComplete has a special aqString scripting object. The object is available for all supported scripting languages, so that you can use it to operate with string values regardless of the chosen language.

Another scripting object that is useful for string manipulation is aqConvert. This object has several methods that convert values of different types to a string representation and vice versa.

Furthermore, Python has its own inherent object, string, which is a wrapper for the string data type. Strings that are used in TestComplete are compatible with this object. Moreover, string objects are created implicitly for every string. That is, you can call object methods not only for object instances but also for any TestComplete string. For example, the following method call is correct:

A detailed description of the string object is provided in Python Wiki. The table below lists the object's major properties and methods:

There are several pairs of symbols used to represent special characters in Python strings. All of them start with a backslash character (\), and are often called escape characters. The following escape characters are allowed in Python.

In Python, you can prefix a string with a special character to specify the way in which it will be processed. In TestComplete, you can use only one prefix for a string. If you need to process a string in multiple ways, process it several times, or use Python methods to convert it.

To obtain the total number of characters in a string, you can either call the len Python method, or the aqString.GetLength method. The character position in Python strings is zero-based, so the maximum position number in a string is Length-1. The code below demonstrates both ways of obtaining the string length:

def StringLengthDemo():
  aString = "Some text"
  Log.Message("The string is " + str(len(aString)) + " character(s) long.")
  Log.Message("The string is " + str(aqString.GetLength(aString)) + " character(s) long.")

Using TestComplete, you can limit the length of string parameters returned by functions of the tested application. For this purpose, use the Maximum string length of [out] parameters project property. If the length of the string returned from the application via one of its out parameters exceeds the property’s value, TestComplete treats the returned string as a null one.

Several strings can be concatenated to form another string. The aqString object has a special (aqString.Concat) method that performs this operation.

However, it is more convenient to use the addition operator (+) for this purpose. To append an numeric value, convert it to a string by using the str method.

The sample code below demonstrates how to use all three techniques:

def ConcatenationDemo():
  Str1 = "String No 1 "
  Str2 = "String No 2 "

  Log.Message(aqString.Concat(Str1, Str2))
  Log.Message(Str1 + "String No 2 " + "String No " + str(3) + " ")

You may often need to compare two strings during testing. Generally, a test procedure obtains text data (user input, file contents, property value and so on) and then compares it with the expected data. In Python, the comparison operator (==) can check if the strings are identical. For the TestComplete aqString object, there is the aqString.Compare method.

The aqString.Compare method has three parameters: two of them, String 1 and String2, specify the strings to be compared, while the last parameter defines whether the comparison should be case-sensitive or not.

Both approaches can be used to compare strings containing national symbols, for example, characters with diacritical marks ( , , and others).

The code below demonstrates how to use both approaches:

def StringComparison():
  # Using the method of the native String object
  if "Abra" == "abra":
    Log.Message("Abra is equal to abra")
  else:
    Log.Message("Abra is not equal to abra")
  if "abra" == "Abra":
    Log.Message("abra is equal to Abra")
  else:
    Log.Message("abra is not equal to Abra")
  if "abra" == "abra":
    Log.Message("abra is equal to abra")
  else:
    Log.Message("abra is not equal to abra")

  # Using the method of the aqString object
  Log.Message("aqString.Compare(\"Abra\", \"abra\", False): " + str(aqString.Compare("Abra","abra", False)));
  Log.Message("aqString.Compare(\"Abra\", \"abra\", True): " + str(aqString.Compare("Abra","abra", True)));

  # Dealing with native-language characters
  # The following code assumes that French layout is installed on computer
  
  # French layout
  LangID = 0x040C
  LocaleID = "0000040c"
    
  if aqEnvironment.IsLanguageSupported(LangID) and aqEnvironment.SetKeyboardLayout(Sys.Process("TestComplete").Id, LocaleID):
    
    if "français" == "Français":
        Log.Message("français is equal to Français")
    else:
      Log.Message("français is not equal to Français")
    if "français" == "français":
      Log.Message("français is equal to français")
    else:
      Log.Message("français is not equal to français")
    if "français" == "francais":
      Log.Message("français is equal to francais")
    else:
      Log.Message("français is not equal to francais")
 
    Log.Message("aqString.Compare(\"français\", \"Français\", False): "+str(aqString.Compare("français", "Français", False)))
    Log.Message("aqString.Compare(\"français\", \"Francais\", False): "+str(aqString.Compare("français", "Francais", False)))
    Log.Message("aqString.Compare(\"français\", \"Français\", True): "+str(aqString.Compare("français", "Français", True)))

The Python scripting language does not have a data type used for storing single symbols. However, it is not a problem, since strings can contain series of characters and individual characters. You can access any symbol in a string by specifying its valid index. Moreover, you can extract a single character from a string using the aqString.GetChar method. The sample routine below demonstrates how to extract symbols from strings. It posts text to the TestComplete log in two different ways: as a whole string and by single letters.

def StringByLetter():
  aString = "Per aspera ad astra"
  Log.Message("The string is : " + aString)

  Log.Message("And now this text letter by letter using aqString.GetChar:")
  for i in range(0, len(aString)):
    Log.Message(aqString.GetChar(aString, i));

  Log.Message("And now this text letter by letter using Python syntax:")
  for char in aString:
    Log.Message(char)

One of the most common tasks that you may need to perform when working with string values is determining whether specific text is part of a string. To perform such tasks, use a conditional statement or the aqString.Find method. If the specified substring was found, the method returns the number of the first occurrence of the substring within the source string. If the specified substring was not found, the method returns -1:

def StringOccurrenceDemo():
  aString = "Per aspera ad astra"
  aSubString = "astra"
  Res = aqString.Find(aString, aSubString)
  if  Res != -1:
    Log.Message("A substring '" + aSubString + "' was found in string '" + aString + "' at position " + aqConvert.IntToStr(Res));
  else:
    Log.Message("There are no occurrences of '" + aSubString + "' in '" + aString + "'.")

You can also get the position of the specified substring by using Python's native find method. If the substring was found, the method returns the initial position (from 0) of the first substring match. If no occurrences were found, the method returns -1. The code below demonstrates how to do this:

def TextPosDemo():
  aString = "Per aspera ad astra"
  aSubString = "astra"

  findpos = aString.find(aSubString)
  
  if findpos != -1:
    Log.Message("A substring '" + aSubString + "' was found at position " + str(findpos))
  else:
    Log.Message("There are no occurrences of '" + aSubString + "' in '" + aString + "'.")

Python strings can be accessed as arrays. This means that to get a substring, you can just use the array syntax ([x:y]).

TestComplete provides the aqString object that has the SubString method. This method returns the text fragment between the starting and ending character positions. The character at the ending position is not included. The position is zero-based. If the starting position is greater than the ending position, then these values are swapped. Negative values are considered as zeros.

The sample code below demonstrates how to use these approaches:

def GetStringDemo():
  Str = "0123456789";

  Log.Message("The Python array syntax demo:")
  Log.Message(Str[2:7]) # Posts "23456"
  Log.Message(Str[7:2]) # Posts "23456"
  Log.Message(Str[-2:7]) # Posts "0123456"
  Log.Message(Str[2:2]) # Posts ""

  Log.Message("The 'aqString.SubString' method demo:")
  Log.Message(aqString.SubString(Str, 2, 5)) # Posts "23456"
  Log.Message(aqString.SubString(Str, 2, 0)) # Posts ""

Sometimes, you may need to make several strings out of a single string. This operation splits a string into substrings. This can be done by using the Python split method. This method searches the string for delimiter characters (defined either as a string or a regular expression), splits the string and returns a list containing the resulting strings. Also, you can limit the list length using the third parameter. It is optional and can be omitted. The same method can be used to split a string into substrings, sentences and even separate words. This depends on the specified delimiter. The first sample routine below uses a space character as a delimiter to extract words from a string and the second routine splits a string by line breaks:

def SplitDemo1():
    s = "Better late than never but better never late."
    # Split at each space character.
    ss = s.split(" ")
    Log.Message("The resulting array is: " + str(ss))
    Log.Message("There are " + str(len(ss)) + " words in the array")
    Log.Message("The first word is: " + ss[0])
    

def SplitDemo2():
    s = "Better late than never\r\nbut better never late.";
    # Split at line break character.
    ss = s.split("\r\n")
    Log.Message("The resulting array is: " + str(ss))
    Log.Message("There are " + str(len(ss)) + " words in the array")
    Log.Message("The first word is: " + ss[0])

TestComplete has a similar method called aqString.GetListItem. It extracts a substring with the specified index from the input string. It was designed to read items from string lists. See Working With String Lists for more information. However, it also redefines delimiter characters and, like the split method, can be used to get sentences, separate words and so on.

def SplitDemo3():
    s = "Better late than never but better never late."
    # Assign list separator to space character
    prevSep = aqString.ListSeparator
    aqString.ListSeparator = " "
    # Split by spaces
    Log.Message("There are " + str(aqString.GetListLength(s)) + " words in a string")
    Log.Message("The first word is: " + aqString.GetListItem(s,0))
    # Restore previous separator
    aqString.ListSeparator = prevSep

You may need to remove leading or trailing spaces, or both from a string you get in your tests. To do this, use Python's string.lstrip, string.rstrip and string.strip methods and the TestComplete aqString.Trim method.

def TrimDemo():
  str="    Hallo    ";
  Log.Message("'" + aqString.Trim(str, aqString.stLeading) + "'") # Posts 'Hallo    '
  Log.Message("'" + aqString.Trim(str, aqString.stTrailing) + "'") # Posts '    Hallo' 
  Log.Message("'" + aqString.Trim(str, aqString.stAll) + "'") # Posts 'Hallo'

You may also want to exclude extra inner whitespaces from a string. To do this, split the string into separate words and then put the words together separating them with one space character.

def TrimInner(Str):
    WordArray = Str.split()
    Str = ""
    for i in range(0, len(WordArray)):
      Str += (WordArray[i] + " ")
    return aqString.Trim(Str)

#An example of how to use this function
def TrimInnerDemo():
  Log.Message(TrimInner("Follow the      white rabbit"));

You may need to find and replace a character or substring within a string. You can do this in two ways: by using the aqString.Replace method or by using the replace method of a string object.

The aqString object method is much easier to use. It can be used when you need to change certain character or string. It allows you to specify whether the search should be case-sensitive or not. Below is an example that demonstrates how to use this method:

def StringReplaceDemo():
  str = "Hi, Bob. Have you seen Bob Robbinson?"
  str = aqString.Replace(str, "Bob", "Jack", True)
  Log.Message(str)

The String.replace method is more complicated, but it offers more flexibility. You can change not only a character or string, but also all the fragments matching the specified regular expression pattern.

The first sample demonstrates how to change a string using the replace method.

import re
def RegExReplaceDemo1():
  str = "Hi, Bob. Have you seen Bob Robbinson?"
  # Define regular expression pattern
  regexp = "Bob"
  # Perform replace operation
  str = re.sub(regexp, "Jack", str)
  Log.Message(str)

The second example demonstrates how to replace a substring with alternative parts. The patterns of alternative parts are separated by pipe characters (" | "). For instance in the example below, the ht(ml|m) pattern matches both html and htm:

def RegExReplaceDemo2():
  str = "The html is widely used in Internet. The HTM file is a text file with tags."
  # Define regular expression pattern.
  regexp = "(html|htm)"
  # Perform replace operation
  str = re.sub(regexp,"hypertext markup language", str, flags=re.I)
  Log.Message(str)

Furthermore, using regular expressions, you can search for the text fragments matching the specified format. In the example below, all the dates written in the DD/MM/YYYY format are replaced with the Some Date string. This operation can be useful, for example, when comparing two reports that contain the date they were generated.

def RegExReplaceDemo3():
  str = "Date of report: 30/04/2005."
  # Define regular expression pattern.
  regexp = "(\d{1,2}.\d{1,2}.\d{2,4})"
  # Perform replace operation
  str = re.sub(regexp,"Some Date", str)
  Log.Message(str)

The TestComplete aqString object and the native string object have methods that convert uppercase letters to lowercase letters and vice versa. They are: aqString.ToLower, aqString.ToUpper, String.lower, String.upper and String.title.

The code below demonstrates how to use these methods.

def LetterCaseDemo():
  str="The word 'Champagne' is of French origin"
  # Converting to lower case
  Log.Message(aqString.ToLower(str))
  Log.Message(str.lower())
  # Converting to upper case
  Log.Message(aqString.ToUpper(str))
  Log.Message(str.upper())
  # Converting to title case
  Log.Message(str.title())

Some scripting objects, generally, controls like ListBoxes, ComboBoxes, Memos, etc., return information about their state or contents as string lists. The individual data elements (or items) in these lists are separated by commas, line breaks, carriage returns or some other delimiter characters.

The aqString object has a number of specific methods (AddListItem, ChangeListItem, DeleteListItem, GetListItem and GetListLength) that deal with such lists of strings. The AddListItem method adds an item to the list, the DeleteListItem method removes an item from the list, the GetListItem method retrieves the item with the given index, the ChangeListItem method assigns a new value to the given item and the GetListLength method returns the total number of items in the string list.

The symbol that is used as a separator of list items is defined by the ListSeparator property. By default, the list separator is a pipe character "|", but you can also assigned a comma, column, line break, carriage return, tab character or any other printable and non-printable character, or even several characters.

The sample code below demonstrates how you can work with string lists returned by scripting objects.

def ListDialogOptions():
    # Get a string with dialog options
    OptStr = UserForms.UserForm1.SaveDialog1.Options
    # Assign list separator to comma
    prevSep = aqString.ListSeparator
    aqString.ListSeparator = ","
    # Get the number of dialog options 
    Log.Message("The dialog has " + str(aqString.GetListLength(OptStr)) + " option(s) enabled:")
    # Iterate through the options list
    for i  in range(0, aqString.GetListLength(OptStr)):
      #Get the option and post it to log
      Log.Message("Option No " + str((i+1)) + " is: "+ aqString.GetListItem(OptStr, i))
    # Restore previous separator
    aqString.ListSeparator = prevSep;

def ManageMemoText():
    # Get a string with memo lines
    StrList = UserForms.UserForm1.cxMemo1.Lines.Text
    # Post the memo contents to log
    Log.Message(UserForms.UserForm1.cxMemo1.Lines.Text)
    # Assign list separator to newline character
    prevSep = aqString.ListSeparator
    aqString.ListSeparator = "\n"
    # Append one more line 
    StrList = aqString.AddListItem(StrList, "Last Line")
    Log.Message(str(StrList))
    # Change the value of the first line
    StrList = aqString.ChangeListItem(StrList, "New First Line",0)
    # Set the memo contents to a new list
    UserForms.UserForm1.cxMemo1.Lines.Text = StrList
    # Post the memo contents to log
    Log.Message(UserForms.UserForm1.cxMemo1.Lines.Text)
    # Restore previous separator
    aqString.ListSeparator = prevSep