1 / 36

Strings

Strings. Strings. Strings are amongst the most popular types in Python. We can create them simply by enclosing characters in quotes. Python treats single quotes the same as double quotes. Creating strings is as simple as assigning a value to a variable. For example: var1 = 'Hello World!'

gay-morrow
Download Presentation

Strings

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Strings

  2. Strings • Strings are amongst the most popular types in Python. We can create them simply by enclosing characters in quotes. Python treats single quotes the same as double quotes. • Creating strings is as simple as assigning a value to a variable. For example: • var1 ='Hello World!' • var2 ="Python Programming"

  3. Accessing Values in Strings • Python does not support a character type; these are treated as strings of length one, thus also considered a substring. • To access substrings, use the square brackets for slicing along with the index or indices to obtain your substring. Following is a simple example: • var1 ='Hello World!' • var2 ="Python Programming" • print"var1[0]: ", var1[0] • print"var2[1:5]: ", var2[1:5]

  4. output • When the above code is executed, it produces the following result: • var1[0]: H • var2[1:5]: ytho

  5. Updating Strings • You can "update" an existing string by (re)assigning a variable to another string. The new value can be related to its previous value or to a completely different string altogether. Following is a simple example: • var1 ='Hello World!' • print"Updated String :- ", var1[:6]+'Python'

  6. output • When the above code is executed, it produces the following result: • Updated String :- Hello Python

  7. Escape Characters

  8. print"hi" • print"\thi" • print“\\thi” • output • hi • hi • \thi

  9. String Special Operators 1Assume string variable a holds 'Hello' and variable b holds 'Python'

  10. String Special Operators 2

  11. String Formatting Operator • One of Python's coolest features is the string format operator %. This operator is unique to strings and makes up for the pack of having functions from C's printf() family. Following is a simple example: • print"My name is %s and weight is %d kg!"%('Zara',21) • When the above code is executed, it produces the following result: • My name is Zara and weight is 21 kg!

  12. Formatting symbols

  13. Formatting examples print"My name is %s " % ('Zara') #%s string print"My weight is %u kg!" % (21) #%u unsigned decimal integer print"My initial is %c " % ('Z') #%c character print"The temperature is %d degrees " % ( -21) #%d signed decimal integer print"The temperature is %f degrees precisely " % ( -21.34) #%f floating point real number print"big number %e" % 123456789 #%e exponential notation (with lowercase 'e') print"another big number %E" % 987654321 #%E exponential notation (with UPPERcase 'E')

  14. output • My name is Zara • My weight is 21 kg! • My initial is Z • The temperature is -21 degrees • The temperature is -21.340000 degrees precisely • big number 1.234568e+08 • another big number 9.876543E+08

  15. Strings and Raw Strings 1 • Raw strings don't treat the backslash as a special character at all. Every character you put into a raw string stays the way you wrote it: • print'C:\\nowhere‘ • it produces the following result: • C:\nowhere

  16. Strings and Raw Strings 2 • Now let's make use of raw string. We would put expression in r'expression' as follows: • printr'C:\\nowhere‘ • it produces the following result: • C:\\nowhere

  17. Unicode String • Normal strings in Python are stored internally as 8-bit ASCII, • Unicode strings are stored as 16-bit Unicode. • This allows for a more varied set of characters, including special characters from most languages in the world. • printu'Hello, world!‘ • it produces the following result: • Hello, world! • As you can see, Unicode strings use the prefix u, just as raw strings use the prefix r.

  18. capitalize and center str = "this is STRING example....wow!!!"; print"str.capitalize() : ", str.capitalize() str = "this is string example....wow!!!"; print"str.center(40, 'a') : ", str.center(40, 'a') • outputs • str.capitalize() : This is string example....wow!!! • str.center(40, 'a') : aaaathis is string example....wow!!!aaaa

  19. count • The method count() returns the number of occurrences of substring sub in the index [start, end]. • Optional arguments start and end are interpreted as in slice notation. • str.count(sub, start=0,end=len(string))Parameters • sub -- This is the substring to be searched. • start -- Search starts from this index. First character starts from 0 index. By default search starts from 0 index. • end -- Search ends from this index. First character starts from 0 index. By default search ends at the last index.

  20. Example, output? str = "this is string example....wow, WOW, wow!!!"; sub = "i"; print"str.count(sub, 4, 40) : ", str.count(sub, 4, 40) sub = "wow"; print"str.count(sub) : ", str.count(sub)

  21. output • str.count(sub, 4, 40) : 2 • str.count(sub) : 2

  22. Python String find() Method The method find() determines if string str occurs in string, or in a substring of string if starting indexbeg and ending index end are given. • str1.find(str2, beg=0end=len(string)) • str -- This specifies the string to be searched. • beg -- This is the starting index, by default its 0. • end -- This is the ending index, by default its equal to the lenght of the string. • Return Value • This method returns index if found and -1 otherwise.

  23. Find example • str1 = "this is string example....wow!!!"; • str2 = "exam"; • printstr1.find(str2); • printstr1.find(str2, 10); • printstr1.find(str2, 40);

  24. output • 15 • 15 • -1

  25. Python String isalnum() Method • The method isalnum() checks whether the string consists of alphanumeric characters. • str.isalnum() • This method returns true if all characters in the string are alphanumeric and there is at least one character, false otherwise.

  26. Is alpha numeric • str = "this2009"; # No space in this string • printstr.isalnum(); • str = "this is string example....wow!!!"; • printstr.isalnum();

  27. output • True • False

  28. Python String join() Method The method join() returns a string in which the string elements of sequence have been joined by strseparator. • str.join(sequence) • sequence -- This is a sequence of the elements to be joined. • This method returns a string, which is the concatenation of the strings in the sequence seq. The separator between elements is the string providing this method.

  29. example • The following example shows the usage of join() method. • str="-"; • seq=("a","b","c"); • # This is sequence of strings. • printstr.join(seq) • it produces following result: • a-b-c

  30. Built-in String Methods1

  31. Built-in String Methods 2

  32. Built-in String Methods 3

  33. Built-in String Methods 4

  34. Built-in String Methods 5

  35. Built-in String Methods 6

More Related