Lowercase and Uppercase
str_1 = "Hello World"
str_1.lower() # turn all characters to lowercase
str_1.upper() # turn all characters to uppercase
Replace
str_1 = "Hello World"
str_1.replace(" ", "") # return "HelloWorld"
str_1 = "Hello World"
str_1.lower() # turn all characters to lowercase
str_1.upper() # turn all characters to uppercase
str_1 = "Hello World"
str_1.replace(" ", "") # return "HelloWorld"