Python String islower() function checks if all the characters in a string are lowercase then return True else False.
Key Points :
- Return Type: Boolean i.e. True or False
- Parametric Values: No Parameters required
- It is not space-sensitive but case sensitive
- Empty String also returns False.
String islower() Syntax
str_name.islower()
str_name here refers to the input string. And, islower() is inbuilt string function in python.
str_name = "welcome"
print(str_name.islower()) # True
String islower() Examples
Different cases are given below.
Case 1: Every character in a string is lowercase also contains whitespaces/numbers/special characters
str_name = "welcome python user"
print(str_name.islower()) # True
str_name = "welcome 2019"
print(str_name.islower()) # True
str_name = "welcome @ 2020"
print(str_name.islower()) # True
Case 2: Every character in a string is uppercase, also contains whitespaces/numbers/special characters
str_name = "WELCOME PYTHON USER"
print(str_name.islower()) # False
str_name = "WELCOME 2019"
print(str_name.islower()) # False
str_name = "WELCOME @ 2020"
print(str_name.islower()) # False
Case 3: String contains only numbers or special characters
str_name = "2020"
print(str_name.islower()) # False
str_name = "@$&"
print(str_name.islower()) # False
Case 4: Only the first character of every word is uppercase, also contains whitespaces/numbers/special characters
str_name = "Welcome"
print(str_name.islower()) # False
str_name = "Welcome Python User"
print(str_name.islower()) # False
str_name = "Welcome 2019"
print(str_name.islower()) # False
str_name = "Welcome @ 2020"
print(str_name.islower()) # False
Case 5: String is Empty
str_name = ' '
print(str_name.islower()) # False
Program to Print List of All Possible Lowercase Characters in Python
The Unicode module can be used to check the lowercase characters. The program is to print all lowercase Unicode characters.
import unicodedata
total_count = 0
for i in range(2 ** 16):
charac = chr(i)
if charac.islower():
print(u'{:04x}: {} ({})'.format(i, charac, unicodedata.name(charac, 'UNNAMED')))
total_count = total_count + 1
print("Total Number of Lowercase Unicode Characters = ",total_count)

It is just a glance of output as the actual output is lengthy. There are 1402 Lowercase characters in Unicode.
References
- Python String islower()
- Python Built-in Functions