Basic data type supplement

str:

title case

name = 'alKx'
name1 = name.capitalize()     # title case
print(name1)

Capitalize initial

name = 'alex haha'
name1 = name.title()     # Capitalize initial
print(name1)

Case reversal

print(name.swapcase())      # Case reversal

Center, center fill

print(name.center(20, "*"))       # Center, center fill

Splicing

print("-".join(name))     # Splicing, splicing with contents in quotation marks, key points

lookup

print(name.find("x"))      # lookup
# From left to right, only one is found, and - 1 is not returned.
print(name.index("x"))     # Index. In some cases, the index position is returned according to the position of the string. If not, the throne

Format

# %s
# f
# Fill in sequence position
name = "alex,{}, {}, {}"
print(name.format(1,2,3))      # tuple

#Fill in by index value
name = "alex,{2}, {0}, {1}"
print(name.format(1,2,3))

# Fill by key
name = "alex,{a}, {c}, {b}"
print(name.format(a=11, b=22, c=99))

list definition method

list("123")

Other methods

Sort (default ascending)

lst = [1,2,23,234,435,36,23,213421,421,4231,534,65]
lst.sort()
print(lst)

lst = ["Hello","I am good."]
lst.sort()
print(lst)

Descending order

lst = [1,2,23,234,435,36,23,213421,421,4231,534,65]
lst.sort(reverse=True)     # Descending order
print(lst)

Reversal

lst.reverse()
print(lst)
Another way
print(lst[::-1])
#Reverse, reverse; or use [:: - 1]

Sort before reverse

lst = [1, 2, 3, 4, 5123, 21345, 231123, 4, 1235, 234, 123]
lst.sort()
lst.reverse()
print(lst)
# First sort, then reverse; first sort, then reverse;

Interview questions

lst = [[]]
new_lst = lst * 5
new_lst[0].append(10)
print(new_lst)
# The first level element is modified, so the source list is modified, and the new list is also changed.

lst = [1,[]]
new_lst =lst * 5
new_lst[0] = 10
print(new_lst)
# The first level element of the new list is modified, and the source list is not modified.

lst = [1,[]]
new_lst =lst * 5
new_lst[1] = 10
print(new_lst)
#Principle is the same as above.

Merge two lists

Method 1:
lst = [1]
lst1 = [2]
lst.extend(lst1)
print(lst)

Method two:
print(lst + lst1)

Lists can be multiplied by numbers

lst = [[]]
new_lst = lst * 5
new_lst[0].append(10)
print(new_lst)

tuple

The data type is () the data itself in brackets
 Adding a comma is a tuple. Adding two commas will result in an error.
A tuple is an immutable list, which can be added, multiplied, not shared, or both.

tu = (1,)   # (1,) is a tuple
print(type(tu))

dic

The dictionary is out of order. Define a dictionary

print(dict(key=1, key2=2))

Randomly delete popitem

dic = {"key":1, "key2":2}
print(dic.popitem())     # Random deletion, which returns the deleted key value pair
print(dic)      # Python 36, delete the last one by default

Batch addition

dic = {}
dic1 = dic.fromkeys("123",[23]) 
print(dic1)
# Batch add key value pair {"1": [23], "2": [23], "3": [23]}

dic = dict.fromkeys("123", [23])
dic['1'] = [5]
print(dic)
# Batch add key value pairs {'1': [23]}, '2': [23], "3": [23]}

dic = dict.fromkeys("123456789",1) 
dic["1"] = 18
print(dic)
# To batch add key value to "key is an iterative object", the value -- will be shared

set

set() --- empty set
 {} ------ empty dictionary
 Define set:
set("alex") (add iteratively

# bool: False
# Number: 0
# String: ''
# List: []
# Tuple: ()
# Dictionary: {}
# Set: set()
# Others: None

split cuts out a list.

Type conversion between data

list  tuple
tuple list

# str list
name = "alex"  print(name.split())

# list str
lst = ["1","2","3"] # print(''.join(lst))
split It's a list.

# dict -- str
dic = {"1":2}
print(str(dic),type(str(dic)))
print(dict("{1:1}"))
//Convert list to string