Python Lower and Upper: Capitalize StringUse the lower, upper, islower and isupper methods. Call title and capitalize.
Lower, upper. All letters are either lowercase or uppercase. We can change the case of characters in Python with the lower and upper methods.
String casing. More powerful methods such as capitalize and title() also exist. We cover the basic methods (upper and lower) first, and then explore isupper and islower.
Tip: We never need to call upper() on a string that is already uppercased. Please see the isupper and islower methods.
Python program that uses upper, lower value = "Tree" # Uppercase the string. x = value.upper() print(x) # Lowercase the string. y = value.lower() print(y) Output TREE tree
Also: Please see the performance test. Is lower is used to improve speed. With it, we can avoid copying strings.
Python program that uses isupper, islower value1 = "ABC123" value2 = "abc123" # Method can be used in an if-statement. if value1.isupper(): print(1) # Call methods on both strings. print(value1.isupper()) print(value2.isupper()) print(value1.islower()) print(value2.islower()) Output1 True False False True
Here: Please notice that the variable "s" is assigned to the result of capitalize().
Tip: This means capitalize() does not change the existing string in-place. It creates a new copy of the string in memory and returns that.
Python program that uses capitalize# An input string. s = "perls" # Capitalize and assign. s = s.capitalize() print(s) Output Perls
Warning: Title will capitalize words that are not supposed to be capitalized, like "of" and "and."
Thus: A custom implementation (not the title method) would be needed if your requirements are more complex.
Python program that uses title string method value = "the unbearable lightness of being" # Convert to title case. result = value.title() print(result) Output The Unbearable Lightness Of Being
Note: As with the title method, istitle will become confused on certain words. It requires all words, even "and" to be capitalized.
Python program that uses istitle value1 = "A Car" value2 = "A car" value3 = "a Car" value4 = "A123" value5 = "a123" # Test istitle method. print(value1.istitle()) print(value2.istitle()) print(value3.istitle()) print(value4.istitle()) print(value5.istitle()) OutputTrue False False True False
Version 1: This version of the code calls the lower() method on every iteration through the loop.
Version 2: This version uses islower() before calling lower(). It never calls lower() because the string is already lowercase.
Result: The code that checks islower() first is faster. This optimization will only work if your data is usually lowercase.
Python program that benchmarks islower, lower import time value = "intuitive" print(time.time()) # Version 1: lower. i = 0 while i < 10000000: v = value.lower() i += 1 print(time.time()) # Version 2: islower and lower. i = 0 while i < 10000000: if not value.islower(): v = value.lower() i += 1 print(time.time()) Output 1384626116.650 1384626122.033 lower(): 5.38 s 1384626124.027 islower() and lower(): 1.99 s
Lower dictionary. We can use a dictionary to avoid lowercasing the same string many times. This can speed up the lowercase operation—the cache may be 10 times faster.Lower Dictionary
A summary. Text processing often involves normalizing the casing of strings. With the lower method and its friend upper(), we do this.
Testing cases. Performance is improved in many programs by using islower() and isupper(). This reduces work but may introduce complexity.Strings
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