String

Chain string operations

info = "  John Doe, 30, New York  "
formatted_info = info.strip()
formatted_info = formatted_info.upper()
formatted_info = formatted_info.split(',')
print(formatted_info)  # ['JOHN DOE', ' 30', ' NEW YORK']

# chained operations
formatted_info = info.strip().upper().split(",")
print(formatted_info)  # ['JOHN DOE', ' 30', ' NEW YORK']

''.join() when creating a single string for list elements

list_of_strings = ['Hello', 'World']
joined_string = ''.join(list_of_strings)

# vs
res = ''
for string in list_of_strings:
    res += string

Case Conversion

• lower(), 'HELLO WORLD'.lower() # 'hello world'
• upper(), 'hello world'.upper() # 'HELLO WORLD'
• title(), 'hello world'.title() # 'Hello World'
• capitalize(), 'hello world'.capitalize() # 'Hello world'
• swapcase(), 'HeLLo'.swapcase() # 'hEllO'

Searching and Counting

.find(sub[, start[, end]])

'hello world'.find('world')  # 6

.rfind(sub[, start[, end]])

'hello world world'.rfind('world')  # 12

.count(sub[, start[, end]])

'hello world'.count('o')  # 2

Trimming and Padding

.strip([chars])

'  hello world  '.strip()  # 'hello world'

.lstrip([chars])

'  hello world  '.lstrip()  # 'hello world  '

lstrip -

'-42'.lstrip('-')  # '42'

.rstrip([chars])

'  hello world  '.rstrip()  # '  hello world'

.ljust(width[, fillchar])

'hello'.ljust(10, '-')  # 'hello-----'

.rjust(width[, fillchar])

'hello'.rjust(10, '-')  # '-----hello'

.zfill(width[, fillchar])

'42'.zfill(5)  # '00042'

Replacement

.replace(old, new[, count])

'hello world'.replace('world', 'Python')  # 'hello Python'

Splitting and Joining

.split([sep[, maxsplit]])

'hello world'.split()  # ['hello', 'world']

.rsplit([sep[, maxsplit]])

'one,two,three'.rsplit(',', 1)  # ['one,two', 'three']

join(iterable)

'-'.join(['hello', 'world'])  # 'hello-world'

Testing and Validation

.startswith(prefix[, start[, end]])

'hello world'.startswith('hello')  # True

.endswith(suffix[, start[, end]])

'hello world'.endswith('world')  # True

.isalnum()

'hello123'.isalnum()  # True

.isalpha()

'hello'.isalpha()  # True

.isdigit()

'123'.isdigit()  # True

.isnumeric()

'⅕'.isnumeric()  # True

.isspace()

'   '.isspace()  # True

MIscellaneous

len(str)

len('hello')  # 5

ord(char) and chr(codepoint)

ord('A')  # 65
chr(65)  # 'A'

eval()

eval() evaluates a string as a Python expression and returns the result. It can be dangerous if used with untrusted input.

result = eval('2 + 3 * 4')  # 14
result = eval('x + y', {'x': 1, 'y': 2})  # 3
result = eval('x + 2'.replace('x', '2'))  # 4