Python. Strings. Functions and methods

11.2.2.3 apply functions and string processing methods

Python. Strings. Functions and methods

String is a indexed sequence of characters.

Function/Method Example Description

s1 + s2

s1 += s2

s1 = "Hello "
s2 = "world"
s = s1 + s2 
print(s) # "Hello world"

Concatenation of strings means all characters from s1 come first,
and then all characters from s2

s * n

s *= n

s1 = "Ra"
s = s1 * 4 
print(s)  # "RaRaRaRa"

String s repeated n times
s1 in s2

s1 = "own"
s2 = "brown"
print(s1 in s2) # True
print("ron" in s2) # False

Checking that substring s1 is contained in s2
s1 not in s2

s1 = "own"
s2 = "brown"
print(s1 not in s2) # False
print("ron" not in s2) # True

Checking that substring s1 is not contained in string s2
The same as not (s1 in s2)
len(s)

s = "school"
print(len(s))  # 6

String length
s[i]

'school'[2] == 'h'
'school'[-1] == 'l'
s = "star"
print(s[0]) # s
print(s[-3]) # t

i-th element of the string,
negative i - for counting from the end
s[start:stop:step]

s = 'school'

print(s[:2]) # 'sc'
print(s[2:5]) # 'hoo'
print(s[::2]) # 'sho'

Slice a string
s.count(s2, a1, an)

s = "abracadabra"
print(s.count("a"))  # 5
print(s.count("a", 2))  # 4
print(s.count("a", 2, 9))  # 3
s2 = "bra"
print(s.count(s2))  # 2

count() method returns the number of occurrences of the substring in the given string.
s1.find(s2) 
s1.rfind(s2)

s = 'abracadabra'
print(s.find('bra'))  # 1
print(s.rfind('bra'))  # 8
print(s.find('bar'))  # -1

The index of the beginning of the first or last occurrence of the substring s2 in s1 (will return -1 if s2 not in s1)
s.startswith(s2) 
s.endswith(s2)
print('school'.startswith('sc')) # True
print('school'.endswith('ml')) # False

Checking if s starts with s2
or ends with s2

s.isdigit() 
 

s.isalpha()
 

s.isalnum()
 

print('123'.isdigit())  # True
print('12A'.isdigit())  # False

print('abc'.isalpha()) # True
print('ab3'.isalpha()) # False

print('E315'.isalnum()) #True
print('E3 15'.isalnum()) #False

Checking that all characters in string s are numbers,
 

letters (including Cyrillic),
 

numbers or letters
 

s.islower() 


s.isupper()
 

print('hi!'.islower()) # True
print("Uralsk".islower()) # False

print('PY123'.isupper()) # True
print('NuR%2'.isupper()) # False

Checking that the string s does not contain large letters,
 

small letters.
Note that for both of these functions, punctuation marks and numbers give True

s.lower() 

s.upper()

print('Welcome!'.lower()) # welcome!

print('Welcome!'.upper()) # WELCOME!

The string s, in which all letters are converted to lower

or upper case,
are replaced with lower or upper case.

s.capitalize()

s.title()

print('welcome back'.capitalize())
# Welcome

print('welcome back'.capitalize())
# Welcome Back

String s, in which the first letter is uppercase

String s, in which all words will be capitalized.

s.lstrip() 

s.rstrip() 

s.strip()

print('  Welcome!  '.lstrip()) # 'Welcome!  '

print('  Welcome!  '.rstrip()) # '  Welcome!'

print('  Welcome!  '.strip()) # 'Welcome!'

String s with whitespace characters (spaces, tabs) removed from the beginning,
end,

or both sides

s.ljust(k, c)
 

s.rjust(k, c)

print('Comment'.ljust(10, '.'))  
# Comment...

print('Comment'.rjust(10, '.'))  
# ...Comment

Adds the required amount to the left

or right
characters c so that the length s reaches k

s.join(a)

print('  '.join(['Computer', 'science']))
# Computer science

Concatenates (joins) strings from list a through s

s.split(s2)

s = "Computer science"

print(s.split()) # ["Computer", "science"]
print(s.split('e')) # ["Comput", "r sci", "nc"]
print("12:25".split(":")) # ["12", "25"]

List of all words of string s (substrings separated by strings s2)

s.replace(s2, s3)

s = "School"

print(s.replace('o', 'e')) # Scheel
print(s.replace('o', 'e', 1)) # Scheol

String s, in which all occurrences of s2 are replaced by s3
There is an optional third parameter, with which you can specify how many times to replace

list(s)

s = "School"

print(list(s)) # ['S', 'c', 'h', 'o', 'o', 'l']

List of characters from string s

bool(s)

s1 = "something"
s2 = ""

print(bool(s1)) # True
print(bool(s2)) # False

Checking that the string is not empty (returns True if not empty and False otherwise)

int(s) 

float(s)

s = "50"

print(int(s) + 4) # 54
print(float(s) + 4) # 54.0
print(int("54A")) # ValueError: invalid literal for int() with base 10: '54A'

If string s contains an integer or
(fractional) number,
get this number, otherwise it's an error

str(x)

n = 37

print(str(n) + "2") # 372

Convert any object x as a string

 

Questions:

Exercises:

Ex. 1

Ex. 2 Identify result of outputs (Designed by Mr. Halil Mali - CS teacher of NIS Uralsk)

Ex. 3 Identify result of outputs (Designed by Mr. Halil Mali - CS teacher of NIS Uralsk)

Ex. 4 Identify result of outputs (Designed by Mr. Halil Mali - CS teacher of NIS Uralsk)

Ex. 5 Identify result of outputs (Designed by Mr. Halil Mali - CS teacher of NIS Uralsk)

Ex. 6 Identify result of outputs (Designed by Mr. Halil Mali - CS teacher of NIS Uralsk)

Tasks:

Категория: Programming languages | Добавил: bzfar77 (13.12.2021)
Просмотров: 237 | Теги: Lower, Index, String, Upper, capitalize, Python | Рейтинг: 5.0/3
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