Python Data Type: String

Overview

• Strings are a data type in Python.
• Characters enclosed in single or double quotes.

Topics Covered

• Creating strings.
• Converting string cases (lowercase, uppercase).
• Finding the length of strings.
• String operations in bioinformatics (e.g., DNA sequences).

Resources

• Notebooks available on Patreon.
• Google Colab for running code online.

Creating Strings

• Define a string variable: my_string = "bioinformatics".
• Use single or double quotes.
• Print strings using print() function.

String Operations

Creating DNA Sequences

• DNA sequences as strings: my_dna = "AGC".

Converting Cases

• Convert to lowercase: my_string.lower().
• Convert to uppercase: my_string.upper().
• Capitalize first letter: my_string.capitalize().

Finding Length

• Use len() function to find number of characters.
• Spaces are counted as characters.

Checking Substring

• Check presence: 'p' in my_string.
• Case sensitive checks.
• Find index: my_string.find('love').

Counting Characters

• Count occurrences: my_string.count('o').
• Use for biological sequences like DNA.

Replacing Characters

• Replace substrings: my_string.replace('g', 'G').
• Convert DNA to RNA by replacing T with U.

Combining Strings

• Concatenation using + operator: full_name = first_name + " " + second_name.
• String formatting methods:
  • "%s %s" % (first_name, second_name)
  • "{} {}".format(first_name, second_name)

Indexing and Slicing

• Access specific characters or sub-strings.
• Indexing: Start from zero.
• Slicing: Use my_string[start:end].
• Negative Indexing: Access from the end.
• Stepping: my_string[start:end:step].

Bioinformatics Applications

• DNA sequence manipulation using strings.
• Calculate GC content.

Exercises

• Length of sequence.
• Percentage GC content.
• Check nucleotide position.

Conclusion

• Practice is key in mastering Python string operations.
• Explore additional Python string functions and methods.
• Utilize Python for bioinformatics and biological data handling.

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For further exploration, consider looking into regular expressions for more complex string manipulation tasks.