String-operations

This section introduces you to most common (and often very useful) operations for text processing in Python. For a comprehensive list of string operations, please refer to Python documentation. You will find these string operations very useful in different context, for example when re-naming data files, or generating print-messages within your own scripts.

String is a data type that is used for representing text. Within code, strings can be enclosed with single (‘’) or double (“”) quotation marks:

Concatenation

Combining several pieces of text into one variable by adding them together:

# You can concatenate strings
combined_text = text1 + text2

By default, strings and numbers cannot be concatenated. Just try:

#concatenate text and number
number =3.5
text_and_number = text1 + number  # will result in error

Numbers need to be converted into string data type using function str() prior to combining with strings.

#concatenate text and number
number =3.5
text_and_number = text1 + str(number)  # should work!

Slicing and multiplication

# Slice string (extract a substring) based on index
sliced_text = combined_text[0:6]   # --> take 6 letters starting from position 0

# Get the length of the string
len(combined_text)
len(sliced_text)

# Multiply a string:
repeated = sliced_text*4

Insert new line or tab within text

Escape characters are non-printable characters that can be represented with back slash notation. Most commonly used characters are: n (new line) and t (tabulator):

Replacement, Upper-case and lower-case

You can replace words/letters with another one by using a built-in replace function.

# Replace word within text
replaced_word = combined_text.replace('Python', 'Coding')

# Change letters to lower-case / upper-case
upper = replaced_word.upper()
lower = replaced_word.lower()

%-operator

• %s –converts numbers into text
• %f –rounds decimals into a desired length and converts the value into text

text = "value"
number = 5
decimal = 3.14159265359

#Formatting strings:
result = "%s  %s" % (text, number) # % automatically converts the number into text
print(result)
result = ""%s is %s" % (text, number)
print(result)

#Rounding decimals
result = "%s  %.2f" % (text, number)
print(result)